Some thoughts in light of your post and this comment:

Obviously reproductive capacity and production of gametes is a major aspect of sex, but sex goes beyond reproduction as well. As many other GC, scientists, and doctors have said before, sex influences all levels of your biology, effecting every cell, effecting your physical and mental functioning. The way disease manifests differs from males to females. Different symptomologies, needs, treatment efficacities, etc. Even the ability of your cells to differentiate between male and female occurs in utero and is not a simple 'male/female' switch, but a complex biological cascade. And then, this development effects far more than just the gametes you produce.

So, even if gametes could be completely artificially lab-made and 'pregnancy' be conducted in tubes in institutions a la Brave New World, material sex based reality still has obvious and measurable impact on our lives.

I also think that artificially changing these cells is not a good argument for a male body producing female gametes because it's not the male body doing that, it's a transhumanist sci-fi idea that fails to take the intricacies of pregnancy and child-mother bonding into account among other factors. And, the male body could not magically support pregnancy either. Gametes are one aspect of sex, but a condition that destroys your ability to carry gametes doesn't change your sex. Not every female reproduces, this doesn't mean she isn't female.

It's strange that QT seeks to abolish such a basic principle of life, particularly with these hypothetical "thought experiment" questions, all the while advocating to enforce stereotypical social constructs of gender. Especially when there are so many concrete questions that could and should be addressed concerning these concepts. It's a bit baffling.