His unemotionality. The way he speaks formally. His precise mannerisms. The way he always seems to be putting on a facade, like he’s an alien pretending to be human.
I don’t think he was intended to come across as autistic, he just vaguely seems like it.
Native French speaker here - “C’est la vie autiste” would work better I think.
“C’est la vie de l’autiste” would mean “This is life for the autists” - which, to me, has a slurry connotation.
“C’est la vie autiste” would mean “This is autistic life”