When you think about how sexuality actually works, when you go to the mall and see an attractive woman, her genitals are NOT the first thing you notice (hopefully not oh god oh fuck) but you notice their secondary sex characteristics

You have no idea what's in their pants or what they identify as, you either find them attractive or you don't

now whether you would choose to have a sexual or romantic relationship with someone once you do know their identity or biological sex is probably what determines your actual sexual identity, but you can't fault straight girls for unknowingly being attracted to a masculine and powerful transman and while that probably is super rare, how would they have known otherwise