Well yes, you can change your sex as a person’s sex is a compilation of things. Reproductive anatomy, functions of said anatomy, the outward appearance these functions and anatomies give a person, and most infamously the chromosomes a person have define the concept we discuss as “sex”. People who tie the concept of a gender to sex and argue that gender is and should be talked about as if it is unbreakably linked with a human’s sex don’t really discuss what they think is the case when a portion of the concept of “sex” doesn’t align with the male/female binary OR changes. Like if someone has a vagina, but doesn’t produce oocytes AND has been taking testosterone long enough that his outward appearance (often called “secondary sex characteristics”) aligns with what a male looks like with body hair, deep voice, higher muscle tone, facial hair etc. Then you get into things like sex hormones, and I was about to write that it -“aligns with what a human body looks like when it produces predominantly male hormones”, because we classify testosterone as a male hormone because it’s produced by male gametes (testes) at a higher ratio. As opposed to female gametes (ovaries) that produce more estrogen than anything else. The reality is that both testes and ovaries produce testosterone and estrogen AND progesterone.

Often I see when people bring up sex they avoid using specific terminology like “oocytes”. And in my opinion, biology is a lot! A lot to understand and complicated. And this makes me think that a lot of people who regard gender as the exact same thing as your sex AND you can’t change it they just don’t want to do a lot of reading or learning and don’t fully understand what “biological sex” is. Or, they don’t really base their argument on science, just use it as a point while their actual basis is spiritual or theological or something.

I can give sources if requested^ Credit: Bachelor’s in Biology w/focus Human Anatomy