So, a big thing about mental health diagnoses in general is that they have two components: an identifiable behavioral difference from neurotypical baseline, and enough difficulties and social conflict in their life that mental health professionals end up getting involved. The second part is important to keep in mind - people who are like Bill Gross and wind up happily married and running a highly successful bond fund simply do not get diagnosed at nearly the rate as an eleven year old who cannot go through a school day without a screaming meltdown.

This is especially important when it comes to identifying genetic correlations with autism, since anything that negatively impacts overall functioning is going to wind up positively correlated with autism diagnoses. Nobody sane is going to argue that having an itchy skin condition means that you're more autistic, but an autist with itchy skin is more likely to have enough behavioral issues in school to meet the threshold for a mental health referral.

To summarize my point, there's all sorts of genetic stuff that will end up completely unrelated with being autistic, but will end up correlated with getting diagnosed as autistic. This is because merely being neuro-atypical is not enough to get a mental health diagnosis, you need to combine it with enough life difficulties and social conflict to drive the bureaucratic machinery involved with producing a diagnosis.