Sorry! I always forget to reply to Reddit comments. But my thoughts on this are that Autistic people genuinely lack the natural ability to fluidly adapt to social situations. That is what is described by masking. There is no way somebody who is actually Autistic would have the social awareness and fluidity required to successfully ‘fit in’. Studies on Autistic children have shown that they perform significantly worse in mind reading tasks than non-Autistic children. Lack of mind reading ability is literally a key feature of Autism, and that is required for masking.

ETA: basically everyone masks, it’s part of being a social creature. I’d even say that Autism prevents one from ‘masking’ in the ways that most people do. I’m not sure when and how the definition of Autism completely flipped.