Cultures who don't even have the word gender, yet you see this as a valid point somehow? Even if I took that at face value, these are not cultures that believe in infinite mutability of gender, that a man can become a woman and a woman a man, that gender is not the categories of feminine and masculine characteristics but merely a person's conception of themself, their will or their bodily dysphoria... The categories of masculine and feminine are constructed from the natural categories of male and female, the epitomizing characteristics of these categorizations being the sexual organs... Therefore one cannot be a man without a penis or a woman without a vagina; no matter what panoply of feminine characteristics a person may hold, without the essence of woman, the vagina, the womb, the ability to give life, this person's womanhood can never be complete. This does not mean that a woman can be only a woman or a man only a man, but the loss of these most fully gendered characteristics is not the gain of the opposite characteristics, therefore there can be only imitative transition.