While I don't play Rust, my impression is that the devs are being dicks (heh) for what looks to be ideological reasons. They say:

"Technically nothing has changed, since half the population was already living with those feelings. The only difference is that whether you feel like this is now decided by your SteamID instead of your real life gender."

They are wrong, of course, what changed was that there was no choice possible and now there is a choice (which they dangle in front of you and then deny to you).