It doesn't really matter if offense wasn't intended, this is a form of othering that should be corrected and not done again. This is like when you're reading a novel and enjoying the plot when suddenly the narrator chooses to describe a person as "Indian" or "Asian" (people seem to find more creative ways to describe a Black person lol) when everyone else so far is just implied to be white. Only if you're white will you barely notice this, but for the rest of us it definitely changes the whole game. As a society we've done a decent job to be more inclusive of (white, cis, middle-class) women, but that seems to be about as far as we'll go.
I'm not really in trans spaces all that much, but I do know a lot of women take issue with being called "female" (one reason being the dehumanizing aspect of it, especially in the context that it seems to be the term preferred by angry incels). I imagine those who have decided to come out as trans have been in enough of these discussions to refer to themselves as either a man or a woman (if they're not identifying as non-binary), not a male or a female.
