Oh, sorry - it was hard for me to follow your comment as well, but here's my understanding:

We read about OP sharing nudes with a friend.

TERF warns OP that they are sharing nudes not with a fellow woman, but with a man (TERF is assuming friend was a trans woman, assumes OP is a cis woman).

We expect OP to reveal they are actually a trans woman, but instead we learn OP and his friend are cis men.

Does this seem right?

Sorry, these moments make me feel like I must be autistic or something, lol