I went from being "bisexual" and fairly feminine to being totally aromantic yet straight in most of high school, then figured I was bisexual over the summer after Grade 12, tried forgetting it and temporarily joined a cult, went through another strange year, then I really came out to some people I knew as bisexual, realized it wasn't quite right, found out what Pansexuality was, and I totally clicked with it... As I became openly attracted to men, I realized I still had some issues to deal with, I started wearing makeup, realized I was never a "dude", but I felt sorta "gay", but not masculine at all, then I came out to my family as "androgynous" etc... That didn't go over well on my Mom's side... Over about a month or so I came to the slow realization I'm a transgirl, I started going to counselling regularly... Time has passed, I'm moving out very soon... I've had quite a journey.
I'd say it's totally possible for someone to think that, but I mean, most gay dudes I know don't have gender issues, except for my FTM friend