I don't understand the height point. Should everyone under 5'5" be considered female and everyone over, male?

If you're suggesting people in gender egalitarian societies should all look alike, I don't think that's anyone's argument. The point of egalitarianism is that we do not use differences to discriminate, not that we deny their existence. That, in fact, is one of my greatest disagreements with the gender theorists who want to mash men and transmen into one group and women and transwomen into another. We need four groups at least.