It's possible you know more male-to-female trans people than you realize. Male puberty features many irreversible changes, such as a deepening of the voice. Consequently, trans women have a much harder time passing as women, so they are more likely to be out as trans.
It's possible, but the amount of trans men I'd have to not-know-I-know would have to be pretty large to offset the number of trans women, which seems unlikely. I know lots of trans women in my community, and I can't think of a single trans man. Might be specific to my sphere tho.
I think it's specific to your sphere. I heard someone observe that they used to know only way more trans men than trans women in their hippie activist community (Portland?) then when they moved to bay area tech/rationality scene, the ratio flipped to >95% the other way.