I do think mental habits, emotions and emotional patterns are often reflected in the body (general body, posture, and facial tension).... e.g. think about how your shoulders get sore if you are nervous or tense. If you do that a lot (i.e. if being tense is a common emotional pattern for you), you develop strong shoulder muscles, and this affects how the whole musculature hangs together, and how your nervous system starts using your musculature. Or think about how people slump when depressed, collapse into a sort of protective stance when scared, etc. Its def not a science, but there are general "vibes" or patterns you can learn to read in posture and musculature.
In my observation, people (both NTs and spectrum) vary widely in their ability to read these stance differences.
And man, autism is a pretty strong trip as far as the mind goes, so imo it should come as no surprise there's a physically recognizable component.
Personally, I very much think there is a posture "smell" to autism, and some people are sensitive to it, mostly subconsciously, and yeah, it probably can have a bit of an uncanny valley effect.
The good news is that some people LIKE it, especially other aspies (esp those who don't hate themselves lol!).... so in some sense you're signalling who you really are, and people can respond to that... hopefully people who really dig you

Funny thing is, since I'm both autistic & a Taurus (about to hit 34 this week), I'm a very calm & quiet individual a lot of the time. I've had maybe 5 women that cuddled with me & told me I smelled good (even though I don't think I did), and told me I'm a good pillow and that they liked the fact that I was. I can be a very charming guy if I wanted to be, or if I knew a woman had an interest in me besides being friends.