Hm. that is a problem.

or, maybe its not as much of a problem as we think. see, where we currently are right now, we don't HAVE any lava release users nor have we hammered out the history of said lava users. nor is the ninja clan's habit of keeping their jutsu secret conducive to to figuring out whether these four different things really are all the same thing with different applications or four different things that just so happen to share the same combination. after all, its possible that they are different bloodlines that are somewhat related, but its also possible that every lava release user can do all the listed stuff but just doesn't know HOW because they are in different nations who fight against one another and one is a freaking tailed beast who hates humanity in general, so even if it was all the same lava release, there is a lot of reason why enemy users of the same kekkei genkai would not know how to do the things the other can do. especially when one of the things ninjas used to do was intentionally spread false information about their abilities which is what led to people fantasizing and romanticizing them up in the first place.

but lets figure this out from an in world perspective: these are clans and bloodlines. yet they're fighting against one another in different nations. What causes that? If it was a simple matter of them all being different and knowing it, there wouldn't actually be that much competition- they'd just call one "ash release" another "quicklime release" a third "rubber release" since they can't really do the other parts of the release no matter how hard they try, and this split would occur LONG before the modern times of the ninja world, these are bloodlines that have been fighting for probably centuries as the bloodlines fractured off from Indra and Asura. if the bloodline was split three ways the three clans in question would have less reason to fight each other since eliminating one clan and learning their techniques wouldn't help them over any other clan they do it to. however instead all called lava release. which means that at the time this kekkei genkai was discovered people could tell that this is all an extension of the same ability to manipulate lava. so either ninjas collectively decided to classify them all as one release but different bloodlines when they figured out geothermal science (unlikely given the secretive, backstabbing and constantly warring nature of the shinobi world, and why bother when they all do different mutually exclusive things anyways? its not as if shinobi scientists work in a united community to classify these things, they're beholden to their village)
OR the most probable in my eyes, those three clans were all once one clan that at one point birthed three heirs, all three wanted to be leaders like idiots and somehow caused a three way schism that continues to this day with three clans of the same bloodline constantly trying to outdo each other at one release and also trying to steal each other's techniques like petty children and the reason why they do have such unique styles rather than all being the same is because learning this stuff is HARD, no one but their family can teach them, they can't go to other ninja for advice, revealing these secrets is betraying the military you serve (because the bloodlines aren't just a clan secret, they're a village secret because they contribute to a villages military power, so your doubly screwed if you do this.)

also, just because you have a release and that release can do a lot, doesn't mean you can do all the jutsu that is possible with it. I think thats more interesting than every wood user have the same techniques as Hashirama, or all fire release users being able to do all the same things, because the way jutsu works is that learning set of hand seals doesn't really translate to learning the hand seals of another or how to use it. like just because Naruto has wind release, doesn't mean he could do everything that is possible with wind, he figured out a single technique to use that with and it served him fine. Sasuke and Kakashi both have lightning release, but they never learned or bothered with how to do the things the Raikage could with it despite having the sharingan. heck, Kakashi even went a different direction with the chidori than Sasuke, making the Raikiri while Sasuke developed things like the Chidori Eisou or Kirin. given how Boruto does it, it seems that every generation puts a different spin on their techniques probably because of their children wanting to make their own mark on the world. so I'd say that they are the same bloodline, but it doesn't matter because its the actual techniques that make you strong, the genetics just give you access you still have to train to get this or that technique and you can't shortcut the time it takes to learn such things fast unless you have one of few things:
-multi-shadow clone jutsu and tailed beast levels of chakra
-a dojutsu like sharingan, rinnegan or byakugan
(so basically be born as a privileged brat in Konoha)
-a probable willingness to discard your ethics and morals to do anything to steal these things for yourself, potentially killing and maiming people for your megalomaniacal desires to speed up your jutsu learn times
-be so incredibly lucky that one of said privileged brats decides to give you an eye for some reason
-be some once in a lifetime genius prodigy whose ability to learn this stuff so fast can't be replicated.

like if any of these lava clans actually stole the techniques of the other, their best bet would be to teach their CHILDREN how to do these jutsu so that they can use it competently, the current adult generation would have difficulties because they're past the age where learning new things is easier and thus would probably stick to their usual techniques anyways. its probably one of the reasons why they teach this stuff so young. Naruto has a lot of down to earth concerns like that. so just because they all have the same bloodline and have their techniques in a scroll to learn from, doesn't mean they suddenly do everything that the other clan can, this is supposed to take time, and have generational aspects to it.

they are all the same bloodline, but that doesn't mean as much as one might think and getting a clan that can use all forms of that lava release might take generations and even then there would probably be jutsu that only geniuses or he like can pull off, specialists in certain kinds of lava release that would do this or that for the clan (because before villages the clans worked autonomously and thus they would've had to serve all the functions of a village without being one and thus have medic nins, taijutsu specialists, infiltrators, scouts and so on just on a smaller scale) and that their strength might vary depending on what this current generation of the lava clan learns, what aspects of the release, and so on.

I mean heck, in my mind, Kiri water users are very different from more land-based water users as surrounded by water they wouldn't have as good chakra control even if their techniques are more powerful, while land based water jutsu users would focus more on finesse and efficient use of water so they can do more with less- so it makes sense that three different clans could have the same bloodline but have different ways of using it depending on their history, environment and the creativity of those that use them. it is possible for one lava clan to learn the techniques of the other, but it wouldn't be a casual thing. because its their sacred secret techniques that have kept them alive for generations and they probably hate the other guy for being a rival in their field of expertise and also probably one of their distant relatives in a dynasty like family, so even more reason to hate them.

so yes they are all the same kekkei genkai, but due to Naruto's themes of generational conflict, gradual growth and cycles of hatred, your only as flexible as the jutsu you actually know and can access to learn from a teacher or a scroll, with instant learning locked behind specific bloodlines. (and even then you'd need both lava release and a dojutsu, because the dojutsu cannot replicate the DNA, only help you learn the techniques themselves faster if you have access to them) and any on the fly new jutsu in battle without that has to be a modification of a jutsu you already know that is plausibly small enough to do. chakra users can't do the ATLA bender thing and just improvise their elements on the fly constantly, they have to learn specific methods to do specific things.

thats my logic for it, jutsu doesn't seem something you can just freestyle, because of how specific they are even if the element is super flexible, it only means you have a wider variety of jutsu to potentially learn within it that could grant you more versatility in a way another technique won't, because you need to learn a specific hand signs or chakra molding for this or that. it grants you access to potentially do this or that, but it doesn't give you the skill.