That's one type of autism. The reason it's now called Autism Spectrum Disorder is because there are many very different manifestations, not all of which involve hyperfixation.

I have not seen a better description of what autism might be like at a higher (or lower, depending on whether one’s metaphysics align with materialism or not) level than “investing entire attention in a particular sliver of the experiential buffet”.

Amazing at maths but can’t keep a conversation, holed up at home working out like a maniac all the time, musical genius but incapable in daily life[0]—everyone probably knows one or more of such people, especially earlier in life. Is that another side of the same coin? Is it only when this sliver’s intersection with the multi-dimensional space of social-cultural norms is insufficient that other people tend to get weirded out?

[0] These are only some examples, I am sure there are many other ways it can manifest that are familiar to us but were not really thought of as a byproduct of autism. And, of course, some of these can be caused by other factors (e.g., the working out example could be a symptom of body dysmorphia).