Particularly since things like race and gender are generally speaking major elements of what makes a character a character.
In D&D, race (actually meaning species) has mechanical impact, and so is a major element of what makes a character a character. Gender has no mechanical impact in the game as written.
Whether race (in our current cultural sense) or gender matter depends very strongly on whether or not the society in the game, as portrayed by the GM, cares. And in some games, it has been rendered largely irrelevant - Shadowrun and Deadlands, for example, both make explicit points in their setting materials that what we used to think of as race and gender bias have, for in-game reasons, largely gone away. You are free to play any sort of character, and the game world basically doesn't care.
I think he has a point. Back several exchanges you say, " If you are playing as another gender and nothing in your portrayal actually indicates that, then why are you doing it?"
First: have the words "internal role-play" ever come up around you?
Second: There is a difference between, "nothing in your portrayal indicates that," and "nothing in your portrayal indicates that
to me". He can, in fact, be doing his level best to portray a female character, but if he doesn't push *your* preconception-buttons, you won't get that, now will you? It should not be too much to ask for what those preconception buttons are, if you are going to make a big deal out of wanting them pushed. You talk about him portraying "pertinent facts" without saying what you think is pertinent? Is that fair?
Of course, you missed the dirt simple answer to this. We commonly switch between first and third person in referring to our characters. When using third person, use a feminine pronoun. "My character wants information.
She walks up to the guard..." Boom. Job of making sure everyone knows the gender is done.