So many misconceptions in this writeup.
Here's one: even if it were genetic, there could be triggering environmental factors that trigger the onset of autism (I'm just giving a hypothetical example, not making a claim here).
Wouldn’t susceptibility to those environmental factors be dictated by your genetics?
They specifically said there are environmental factors, and not all of them are known. A few are known though: older parents for example.
For example, 45% reduction in symptoms from fecal transplant: https://news.ycombinator.com/item?id=48158494
> Prior to the study, 83% of participants had "severe" autism. Two years later, only 17% were rated as severe, 39% as mild or moderate, and incredibly, 44% were below the cut-off for mild ASD.
Incredible! Sure, there could be a genetic component to what flourishes, or ever seeded, in one's microflora, but there's definitely some external complexities involved here.