I think that is a matter of state law/regulations (and in states where it is prohibited, I believe it really only goes to the amateur status of the kid still in high school, so it’s not actually prohibited, it’s that the kid wouldn’t be able to compete in amateur (e.g., high school) athletic competitions, which wouldn’t be an issue for a high school baseball draftee).
Or do you mean more from the perspective of you aren’t supposed to be able to use NIL as an inducement to enroll at a specific school (but I think that’s pretty easy to avoid problems with - the contract basically just can’t be contingent on enrolling or living in a certain city)?