It would have taken an overabundance of bravery to label that "pregnant woman".
Testosterone is testosterone, and it makes facial hair regardless of your genitals. I know several trans men who have significantly better beards than I have. They don't need beards to be men, though I think many appreciate the visible confirmation that their bodies now match what they understand themselves to be.
It wasn't really the most pressing thing for the Unicode consortium to do. It's just that they had the asymmetry, and it was easy to fix, so they did.
I had the impression that it was pretty rare. Nothing wrong with it; it appears to work perfectly well. But nonetheless I would have expected it to not occur all that often, since the transition is so much trouble and so important to their well-being.