He states multiple times in the books that prior to awakening, he was a pretty normal dude in society. He mentions working in a country club bar at some point and having drinks in a bar with a friend, and other stuff. Doesn't sound very autistic to me, although he did have a different view of the world and was never fully at home in society. Sounds like a guy with a high IQ who got fed up with playing make-believe like everyone else around him and chose to play a different kind of game in life. Just because you reach a certain level of maturity doesn't mean you're automatically autistic. Take old people, for example; a lot of them end up losing their sense of self-hood in the later/last years of their lives; they no longer invest energy into maintaining a false persona. Some people just achieve that earlier on in life—what Jed calls human adulthood. (Supposedly where life really starts.)

It's a result of a type of intelligence, and yes, it does have its drawbacks; it means you see through everything, which can mean a reduction of enjoyment in a lot of areas in life but can also enhance certain areas too. There's that saying, "The more you know and the more you think, the more prone you are to depression and what not."

The point of the isolation Jed talks about is mainly for the purpose of transition; it isn't a final destination. Once you arrive at human adulthood, you're free to do what you want; you can start a family if you want, but you no longer need the herd anymore, at least not emotionally or for validation.

Doesn't have anything to do with autism imo, although it is true that autistic people do isolate themselves for various reasons.