The spectrum of autism isn’t mild to disabling.
It’s a spectrum of presenting symptoms. What “functional autism” is, is a constellation of symptoms that means you can just about navigate the world as expected by neurotypical people. “Non-functioning” autism or “profound” autism are where the constellation of symptoms makes you unable to function in the world. This is more often than not inclusive of non-verbal autisms and poor motor control autisms.
“Functional” autism can be disabling for the individual in certain conditions - they may be completely unable to read social cues, or be severely impacted by certain stimulatory environments.
Marx’s Capital mentions at one point that the working class in Manchester were reliant on drugs like opium to cope with their insane working conditions and poor life/housing conditions.
It’s not a new thing at all.