It's actually a really simple decision. Males always have an advantage in sports invented to showcase male athletic strengths. The entire reason for creating women's categories in the first place was to allow women to shine. It's the source of the advantage as much as the size of it which is the reason that the category excluded males. Women cannot be men, or match men, no matter how hard they train. Therefore all males should be excluded.
It's simple to determine who is male or female in cases of doubt.
It's fairer to exclude males as a class than as individuals or subgroups.
It only gets complicated because of some people's insistence that female sport can be a consolation prize for men who can't compete, or aren't "really" men, because fairness and a level playing field is optional for women's competition. Disabled men do not compete against able-bodied women (they would beat them in some cases because - male advantage), and having certain DSDs is comparable to having a disability. (Not 46 xy, 5-ARD, though.) Women's sport celebrates exceptional females at any level of competition. A CAIS athlete is neither female, nor exceptional, except in comparison to other athletes with the same condition. Fairness in the competition is more important than an individual's disappointment at not being able to compete.
I'm not haranguing anyone on these boards, I'm referring to the attitude of the sporting authorities. There is evidence of a women's version of the Olympic Games in ancient times, but the modern Olympics was conceived as a celebration of masculinity and the male form. Women were to be decorative, or crown the heroes, not to compete. But Alice Milliat and her friends had other ideas!