I couldn't say how accurate this is given that I couldn't be in there long before noping out myself, but while I was there, I read a headcanon that alpha females have a penis and testicles, but either no uterus/vagina or underdeveloped and useless uterus/vagina. Combine that with the headcanon in a nearby post that alpha females remove their breasts and it sounds like they're just... males. Ignoring transgenderism (which other posts threw cans of worms into) for the moment, it makes the clear implication that only males or male-likes can be dominant, and that having the ability to bear children is a "submissive" thing.
Does that make sense? I dunno, it's 2 AM for me.