Man and woman are genders. Gender is a social construct. Social constructs can change.

The binary norm is recent and only has such prevalence due to colonialist empires imposing it everywhere.

There are both extant and extinct cultures that had this all worked out already. It’s annoying that Western culture refuses to draw from those cultures (or even acknowledge them) as it struggles to catch up with the cultures it previously destroyed while praising itself for being progressive.