I agree they aren't the same thing, but I would say that both sex and gender are impacted by biology so I'm not sure that's a useful dividing line. It's true that male and female are two stable sexual categories, but the details of how you identify sex (and how each sex responds to treatments) ends up being very bimodal[1]. So the social categories of male sex and female sex overlay complicated, individual biological systems.

[1] https://twitter.com/ScienceVet2/status/1035246030500061184

Right, and guess which one transgender people care about.

The transphobic people who inevitably show up in threads like this don't seem to recognize the difference, though.

You're playing with semantics.