[skissane]

> Similarly by referring to a person with XX chromosomes as she

It is worth pointing out that there are non-transgender XX males [1]. They are very rare, but it can happen. If the part of the Y chromosome which contains the SRY (testis-determining factor) gene is translocated to the X chromosome, an individual can be an infertile XX male. I don't think anyone would try to argue that such a person is not actually male (assuming they in fact identify as such), in spite of their XX chromosomes, since their external appearance from birth can be completely male. (XX male individuals vary: some appear anatomically completely male, albeit sterile; others show incomplete masculinisation.)

Biological sex cannot be reduced to chromosomes, although chromosomes can be used as a rule of thumb valid 99.99% of the time. In fact, I don't think there is any one single factor to which biological sex can be reduced; both maleness and femaleness are composites of collections of traits which usually occur together, but none of those traits is absolutely necessary to being of that biological sex. People who talk about biological sex as if it was completely determined by chromosomes are ignorant of the whole story.

[1] https://en.wikipedia.org/wiki/XX_male_syndrome