I am usually super skeptical whenever a parent claims that their child just "is" aggressive or that it happened "all of a sudden". It has to come from somewhere. Almost never is it due to some innate physiological imbalance that needs medical correction, whether it be more behaviorism or some kind of chemical straightjacket.

I'd also say that some "behaviors" (ick, I hate how that word's usually used, see here [https://noisyskinbag.medium.com/6-phrases-from-the-disability-world-that-really-grind-my-gears-70b93dd29eef] for why), such as hand-flapping, don't need to be prevented and the parent just needs to shut up, learn why it happens, and deal with it.

All of what you said is all the more reason we shouldn't divvy up "functioning" based on how inconvenient our autism is for others. Someone like me, who speaks and lives on their own often has more in common with a non-speaking autistic person than meets the eye or than their parent does.