This is because autistism advocacy groups misuse the word mask. It is supposed to refer to extra work you have to do playing a specific persona. E.g. at a party pretending to be a character from a movie or a book. And especially trying to force yourself to become that persona to fit in.

A lot of people in the advocacy space use it to mean basic things like being well behaved or being nice to people. Everybody has to be well-behaved at work. Everybody has to consider the feelings of others etc.

The idea of "wearing a mask" in the sense of being polite is older than the notion of masking in autism. For example, P. G. Wodehouse used it a few times in the 1920s to refer to the social expectations made on aristocratic families. E.g. from 1922:

> I didn’t like the chap, but we Woosters can wear the mask. I beamed a bit.

In this sense everyone masks. In fact they mask almost all the time from the time they get up until maybe the time they go to bad. Masking in autism originally referred to something different that was specific to autism.

The way it's used now it essentially just means "it's harder for me to fit in." Which is true but doesn't tell you anything about autism from a psychological point of view beyond the obvious fact that it's harder for us to fit in.