Well it's a spectrum. All humans are on some sort of spectrum, but being autistic means being on the edge of the bell curve. So, some are just further out there than others.
However, it does confuse me, because, although I share a neuorological trait with "profoundly autistic" people, fact is I have far more in common with neurotypicals than I do with them on the level of day to day experience.
I wonder if some of the more profoundly autistic people out there have other neurological traits that just happen to exist alongside autism. For example, if someone is autistic AND mentally ret*d, they may get labeled as severely autistic, but the issue may be the mental handicap, but it takes on the flavor of autistic behavior. Non-autistic mentally ret*d people just get labelled mentally ret*d.
As for the folks who are intelligent but way out there, yeah it's weird. It may be just that the further you venture from neurotypicality, the more random traits come in, and you never know what you're going to get. Artist, scientist, conspiracy theorist, outcast, eccentric...also comorbid traits like depression and anxiety could destabilize someone.