if they’re talking about autism, there are literally physical differences in the brain that cause things like easy overstimulation. these differences may have some benefits (like more refined pattern recognition) but this is not the case for most things. autistic people lack certain traits that are highly valued in neurotypical society. so autistic people are at a disadvantage because of that value system. this doesn’t make autism “bad”. just bad at meeting our society’s current expectations
all this is to say, physically differing from most people in a way that poses societal disadvantages is definitely a disability. suggesting that it isn’t is harmful. i’m not saying we shouldn’t normalize autism (and other disabilities for that matter). we just shouldn’t pretend it comes with no drawbacks.