I can't believe its up to the transit worker (or rather two of them) to decide whether someone's male or female. Its one the oldest tricks in the book to get your designator changed on your ID "OMG, I just noticed it says M and clearly it should say F" or vice versa and a profusely apologetic clerk. If that's the case it must actually happen from time to time in the cis world. What about a deep voiced cis-woman or a high pitched cis-male? What happens when the wrong designator gets put on their ID. What happens when people gain/lose weight, grow their hair out/cut it short?
Its a stupid and impractical policy...