From what I was told, the word binary in terms of sex, relates to how many types of gamete are required to reproduce.
The fact that there are disorders of development in terms of chromosomes is irrelevant. No one produces a third a gamete.
DSD arguments are meant to make the definition of sex difficult. Because a TRA will ask what are you basing your definition of sex on? And if you say, eg, a vagina, then you get 'what about a woman born without a vagina' argument.
If you say chromosomes, then you get the DSD argument.
Obviously, my favourite (for women) is adult human female. Because the second part of that definition is 'of or denoting the sex who bears eggs'. And the keyword is denoting.
But, the DSD/intersex derail is meant to make the definition of sex, and therefore a woman, linguistically difficult. In order that you can claim anyone can be one. Specifically, a man.
Obviously it doesn't even follow logically, never mind in any other way. But that's the reason.