A lot of the behaviors by which autism is diagnosed (social communication, repetitive behaviors and restricted interests) are fairly high-level behaviors, dependent on a lot of cognitive/neural machinery beneath it. There is an idea out there that convergent behaviors that allow consistent diagnosis depends on this, as the resulting behaviors might results from differences in many different underlying processes, but the result at the higher level can be measured the same.

Analogy: Two programs can produce nearly identical behavior at the UI level, but be implemented very differently. Diagnosis operates partly at the "interface" level, but what happens underneath can differ greatly.

Is high-level behavior the only criteria for diagnosis?

I think the majority of the public would like to better understand how we came into this position. There's nothing wrong with the topic of autism as research, but it's been a political football for so long that there are many reasonable doubts about methodology, diagnosis, and relevance to everyday healthcare. I understand there may be complications with some patients that require medical diagnosis and intervention, but does that not imply there should be a much more meaningful label on those cases than just the broad umbrella term of "autism"?

On one extreme, we have people thinking they're autistic when they're actually just awkward and inexperienced in life. On the other, we have people with epilepsy who prefer the label "autism" even though they're merely correlated. Something is wrong here. Not with the science, but the discussion.