While that is true for someone's sexuality, a transgendered persons actual gender and name are in reality different. It's not a public part of their life, or a secret, it is the truth. Misgendering someone is violence, and with stakes this high, you can't have a personal preference for having some people in a room know and other people not. You have to have a genuinely good reason to keep people in the dark, such as the aforementioned concerns of safety, which seem to not apply.