from this, I understand that JKR believes your sex at birth is the most important determinant of gender',
How can an organisation that theoretically promotes human rights be so dense on the subject of human rights?
Nobody suffers discrimination because of their internal sense of their own gender. They suffer discrimination because gender is imposed upon them, regardless of who they feel they are.
Before full equal suffrage in the U.K. in 1928 nobody got to vote because they didn’t feel feminine.
No woman can control her fertility by simply opting out of being female.
Going on about sex being non binary is completely irrelevant. Even if it were scientifically coherent, it wouldn’t stop discrimination against ‘big gamete people’.