From my lived experience and also from the preprint I love very much https://www.thetransmitter.org/spectrum/untangling-biologica... the autism spectrum is basically a collection of ways a brain can largely work differently than "normal". There's a limited number of these (4 according to current research). It's not that there's just individual small features that manifest in things like eye contact avoidance, over/understimulation, etc. it's that the entire brain will work a specific differently and result in a certain set of symptoms consistent with an autism diagnosis. I feel like autism helps form the basis that other neurological differences happen on top of, because it has such a large impact on how thinking and learning even works in the first place. Even in conditions like schizophrenia, psychosis, etc. you see thought loops or detachment from reality or delusions or any number of those kinds of dysfunctions but it all still happens on a base where there can be basically one of the four autisms; the autism seems to be a difference in the foundation that the rest of the brain is built on top of. It's very fascinating to me (I am very autistic). Of course I don't mean to say at all that each autistic type always results in the same brain function but just that usually other difficulties or differences are less fundamental than how autism changes practically everything.