I'm so sorry that you can simply ignore every single argument made on the argument from authority fallacy. Allow me to help break down some things:
Not all sexually differentiated species are sexed due to XY/XX chromosomes. In fact, in some species genes don't even play a role! (https://en.wikipedia.org/wiki/Sex-determination_system) Hormones play a large role in shaping sex traits in humans. In fact, there are multiple criteria when determining a person’s sex, including chromosomes, genital morphology, gonads, hormones, and secondary sex characteristics. And sometimes these criteria don’t all line up with Euroamerican understandings of binary sex.
The idea that many put of separating "Sex" and "gender" in the idea of a "biological sex" and "social gender" depends on a strict separation of "nature" (or biology) and "culture" which anthropologists have been arguing against for years, essentially saying "you can't do that!"
We can also remember that there's a huge tense and troublesome history between "medical scientists" and people with non-normative bodies and identities. Where the "medical scientists" simply ignore that these people exist and that their definitions are incorrect when you take them into account. It also ignores that the idea of sex being only "male" and "female" and that's it, is actually historically recent and culturally specific and has changed frequently and a lot in history.
We can point out that sex and gender are most commonly assigned based purely on genitals and not chromosomes despite the fact that nearly everyone argues that sex is about their chromosomes. And doctors will frequently intervene and conduct surgeries on an infant if their genitals aren't clearly male or clearly female, not because of any medical reason but because of the social reasons.
Basically, using genetics or the the sole existence of a particular genital type is not how sex is determined in the real world by people despite what many people would like to think. “scientific”/biomedical definitions of sex/gender, are actually usually not defined through rigorous scientific work but from assumptions made by researchers based on Euroamerican cultural beliefs (when they seek to define the terms at all). Culture shapes biology and biology shapes culture, they are not separate things.
But if you really want a biological or medical authority, here