You're right about that. Certainly, the implied scope of the piece means that trans women should be included.

Which forces me to narrow my reading, from "this is a post about policing women" to "this is a post about policing women who face relatively little risk of being ejected from the Woman category," from "Who counts? Everyone!" to "Doing It Wrong? No, everyone* is Doing It Right!"

Cis women can pretty much count on being considered women, even if they are then judged to be Doing It Wrong. Trans women can't count on that; they'll face scrutiny of their identity first, and then, only if they pass that test, will they be judged as women.

* Where "everyone" means "cis women."