Another way to think of this is that 'autism' is a broad series of disorders where individuals do not follow the social-relational cues we expect. There are many ways to violate unspoken social expectations, so there should be many ways to be autistic.

In this setting, it's not unreasonable that any genetic syndrome would be more associated with autism; indeed, it's more interesting to find lesions that have a lower proportion of autistic carriers compared to the general population.