As a quick aside I did like this chapter, it was fun and had some neat background stuff, and showed how Luffy is reacting to his defeat from Kaidou.
As for the sea stone bullet thing...have we considered that sea stone effects devil fruit users differently? Paramecia and Logia fruit users showing different effects from exposure that are along the same vein but not 100% the same is entirely valid, I think.
We know that Seastone makes it so that Logia, zoan, and Paramecia can't actively use their devil fruits while they're touching it, and that it saps their energy. making them tired. A Logia and Zoan are trapped in human form while it's touching them. But a logia has to already be in human form for it to affect them from what we've seen. It will just pass through a logia in mist or fire form. since we know Seastone only affects on skin to skin contact.