Incorrect.
You're ignoring the wording of the ability.
Abilities that let you do something new say "you can...". If, on the other hand, an ability is enhancing something you could already do, it will instead say "when you..."
As an example:
The first sentence is giving you the ability to do something you couldn't before (Help as a bonus action), so it uses "you can".Master of Tactics
Starting at 3rd level, you can use the Help action as a bonus action. Additionally, when you use the Help action to aid an ally in attacking a creature, the target of that attack can be within 30 feet of you, rather than 5 feet of you, if the target can see or hear you.
The second is improving something you could already do (Help a creature Attack), so it uses "when you"
Take another example:
Note the use of 'when you' at the start, because casting Mage Hand is something you can already do.Mage Hand Legerdemain
Starting at 3rd level, when you cast Mage Hand, you can make the spectral hand invisible, and you can perform the following additional tasks with it:
- You can stow one object the hand is holding in a container worn or carried by another creature.
- You can retrieve an object in a container worn or carried by another creature.
- You can use thieves' tools to pick locks and disarm traps at range.
You can perform one of these tasks without being noticed by a creature if you succeed on a Dexterity (Sleight of Hand) check contested by the creature's Wisdom (Perception) check.
In addition, you can use the bonus action granted by your Cunning Action to control the hand.
However, all the subsequent abilities are things you weren't previously able to do, and thus they use "you can".
Now look at the Assassin ability:
At no point does it say "when you..."Infiltration Expertise
Starting at 9th level, you can unfailingly create false identities for yourself. You must spend seven days and 25 gp to establish the history, profession, and affiliations for an identity. You can't establish an identity that belongs to someone else. For example, you might acquire appropriate clothing, letters of introduction, and official- looking certification to establish yourself as a member of a trading house from a remote city so you can insinuate yourself into the company of other wealthy merchants.
Thereafter, if you adopt the new identity as a disguise, other creatures believe you to be that person until given an obvious reason not to.
Thus, unless you are saying that WotC abandoned their writing style for this one ability, we must deduce that this entire ability is something only Assassins can do.
Otherwise it would say something to the effect of "When you use Disguise and/or Forgery kits to craft false personas and documents..." because it would then be something that other rogues can also do, and you merely get a better version of it.
Instead, the ability is clearly written in such a way as to indicate that crafting false personas is something you can only do if you are an Assassin of at least 9th level.