If something is at least understandable, then the question of "is this acceptable?" always raises the question "acceptable to whom?" (Or possibly "acceptable to who?" depending on how acceptable you find that…).
In very formal use?
Probably not. The long-standing and well-attested meanings are either "about intent" or (of an action) "on purpose", and this use does not match one of those, so it is probably best avoided for a while to come.
In very informal use?
Middling. It's a bit shirt-and-tie, but then very informal use is flexible, so you can get away with a lot.
The evidence would seem to say it is, wouldn't it?
The self-help community?
It would appear to be close to compulsory.
Hey, we all get to have an opinion. Generally to take an adjective normally applied to actions and then apply it to people wouldn't upset me much, though I'd likely enjoy it the first time and less-so with later use. Here though I can't help feel that using this word rather than considering that its synonym deliberate already has a sense that applies isn't very… intentional, is it? I can't help but dislike it for that reason alone.
However, that dislike is a preference that doesn't go as far as finding it to be "wrong".
Other audiences are going to vary, but with any jargon that has yet to reach a very wide currency there's going to be a range of opinions out there. An objective answer as to whether it's "correct" or not is impossible, but I'd advise not using such jargon unless either you personally like it a lot (hey, you get to have an opinion too) or your dealing with the specialised context where the jargon offers precision no other term does (which in this case doesn't exist).