Except XX male syndrome is a thing, where externally individuals present male but have female karyotype. So are those people female despite having functional male genitalia? And that’s only one of a myriad of situations where an individual’s chromosomes don’t reflect what their phenotype is like nor their biological reproductive function. Chromosomes are NOT an infallible indicator of biological sex.
Also the text of the law says nothing about chromosomes. It indicates from conception the cells that produce the large gamete are considered female, and cells that produce the small gamete are considered male. No one is producing gametes at conception. It also completely disregards anyone who produces no gametes at all. At best this law has declared everyone to have no biological sex whatsoever.
Ogtha