It's a little more complicated with autism though, because one of the hallmarks of autism is blunted empathy (and no, I'm not saying that we're all sociopaths-lite).
An example I heard from a psychologist--and I'm going to try not to butcher this--is that if you show an autistic child a cookie tin and ask them what they think is in the tin, they'll say cookies. Then you show them what's in the tin, and it's actually toy cars. But if, after showing them toy cars in a cookie tin, you ask them what another person is going to think is in the cookie tin, the autistic child is likely to say "toy cars".
Obvs. most people on the spectrum get better about this as they get older and learn from experience, but I strongly suspect that this sort of thing is what's going on when autistic people 'explain' things. My guess is that this difficulty with affective and cognitive empathy is also what leads to people on the spectrum over-explaining things; since they're not able to make an accurate guess about what other people know or can infer, they give too much information about a thing.