That’s because a “trans man” is actually a woman. Not so hard to figure out if you just stick to the plain truth instead of a convoluted woke lie.
What you really have is two dedicated transvestites, of opposite flavors.
The one with female body parts cannot get pregnant unless the normal female hormones are all in sync. And it has to be maintained throughout pregnancy. And the girly man has to have the original wedding tackle and hormonal balance to get her pregment.
Giving a pregnant woman enough testosterone to get that kind of hairgrowth would likely terminate the pregnancy, and/or play all kinds of developemental havoc with the fetus.
Gaslighting, they are.