Obviously autism != intelligence, but I'd wager a fair amount of people are thought to be "on the spectrum" when really they just have an incredibly high IQ compared to their peers.
Obviously not coming at this from a medical background.
Pretty much all diagnosis criteria include some form of "and these things cause some sort of problems in the patient's life". Even if it doesn't, if someone's school/life/career is going OK, they don't seek out a mental health diagnosis. And IQ is one thing that is positively correlated with all sorts of desirable life outcomes.
Like, one notable anecdotal example of this is Bill Gross, the "Bond King". He found out that he was on the spectrum when he was in his seventies. Basically a psych was talking about Asperger's at a dinner, Bill was like "that sounds like me", and his wife was like "of course, dear".
For the longest time people viewed high IQ (as much as it is an actual distinct thing) as a pure blessing. But more and more is coming out saying like everything else high IQ is a trade off and by increasing IQ you decrease other factors so it would not be at all surprising if major issues are strongly correlated with high IQ.
That said I believe autism specifically occurs up and down the range of IQs and there are generally more people with autism on the low end of the spectrum (it could be equally likely that this is because of the diagnosis bias from the above).
This way anybody proving how ridiculous these conditions are is wrong by default.
it's also not lost on those "professionals" that if you can diagnose enough kids with various unfalsifiable "medical conditions", you're set for life with a steady supply of paying customers in the form of easy-street "patients" you can "treat" without ever having to provide any "cure"
and anybody who questions the validity of a science not based on logical reasoning is obviously autistic themselves and thus doesn't count - real people have this emotional intelligence that you simply cannot understand, silly; you're just thinking too logically and thus you're wrong and if you don't shut up and obey we might have to put you in an asylum (for your own good, of course!) because we're so caring and understanding that I'm almost fainting just from thinking about just how good of a person I am