That's the irony. The whole ideology is dependent upon the existence of sex and upon people knowing it exists.
Even more than that - it's dependent on each sex matching, or aligning with, a gender identity. It's not the GC people who have decided that male sex = man gender, and female sex = woman gender. That's the genderists.
Who, after having introduced this rather regressive concept of 'brains/minds/souls/personalities aligning with bodies' then make a big fuss about how they don't actually align in special people.
Whereas GC views are male sex = any brain/mind/soul/personality and female sex = any brain/mind/soul/personality. No alignment required.
This is why under GI, male people who feel feminine equate that with being female. Never mind that there are female people who wouldn't share single feminine characteristic with them.
If they genuinely believed that a woman was 'a person, male or female, with a particular set of feelings/character traits/brain/mind etc' then they wouldn't see any need to emulate a female body, because being female is no more 'womanly' than being male is.
Yet they clearly don't.