From my perspective it's quite clear.

My great-grandfather was a fairly famous astronomer who lived a happy and successful life and had two children. He was known to be absent-minded, kind of goofy, a "nutty professor." In retrospect, it's clear he had high-functioning ASD.

His son was an engineer who was apparently neurotypical. His three grandsons were all... strange. High-functioning - all engineers and lawyers - but obviously ASD.

And then their grandchildren include about four high-functioning "ASD" types, two low-functioning rocking-in-the-corner-and-humming autistics, and two young children where we can't tell yet. One of whom is my son.

Something in my family is genetic, affects only men, and those genes can express themselves as either what you call ASD or as low-functioning autism.

"Wildly divergent"? I don't believe it. They're all the same genes.