I'm convinced that we have some trains equivalent to gaydar, and it goes both ways, ie to the transitioned and non-transitioned.
Years ago, on New Year's Eve, we met a woman who was speaking to my wife and I. She stated that she was trans and, despite my being entirely pre transition and us not mentioning anything, that I was too and that the sooner that I transitioned the better!
For somebody to clock you (who screams female from every pore) and then ask such questions (rude as they were) suggests to me somebody who is coming to terms with their own trans status