I do not support statements like, "there are no biological differences between a woman and a mtf person"
trans women are women
they are different from cis women, but that doesn't suddenly make them any less of a woman
woman is default trans woman is its own thing
no such thing as "cis woman" except as a rhetorical attempt to try to make the default not the default
what
He is saying "cis woman" is an illegitimate term because the term "woman" applies as default to women who are not trans. You don't need the "cis" descriptor because you don't need to distinguish the default group. You can just call them women.
You do need the descriptor "trans" for transwomen because transwomen aren't really women. They're transwomen.