I agree to an extent - but nobody actually KNOWS you have a vagina do they, before discriminating against you?
Well, the male doctors certainly did. And I was pregnant, so my employers certainly knew. I am sure that some people just assumed, but I do think you are posing a very weak argument that it is about 'presentation and the assumption of sex' and again, as per another poster, your argument relies on transitioned males 'passing'.
And what about females who present as 'butch'? Do you honestly believe that they are not discriminated against just the same?
no actual biological reason women have to be the primary care givers to children
On this, we totally agree. However, due to breastfeeding decisions, and that pesky pay disparity, it most likely is that caring responsbilities fall into the domain of females.