If the person cares at that stage, then they shouldn't be in a relationship together anyway, if they're fine, then great for the both of them.
Didn't respond to the bit I haven't quote of yours as I've already covered that in my previous response to FoxEye.
But this is all I've alluded to, people should talk about these things with the prospective partners, if somebody jumps the gun and assumes previous gender that's nobodies fault but their own. If they discuss it and break up fine, if not fine. If they have a kiss and a cuddle then find out, break up/don't fine. All these things happen, it's not a crime.