It confuses me to no end that my very girly oldest child identifies male, especially since hearing them talk about it, it seems more a rejection of being seen as a sexual object than any desire to be a man.
Even psychiatrists don't psychoanalyze their own children.
Maybe instead of hearing your child talk about it, talk to your child about it. Children aren't clay that you stick in a you-shaped mold and expect them to come out no different from you.
Maybe your "very girly" oldest child identifies as male because that's what they consider themselves to be and your definition of "very girly" isn't the same as theirs.
Do you self-identify as male? Do you wear any colors other than grey? Congratulations, you're "very girly" according to the first half of the 20th century.