Must be pretty unprecedented that judges would interpret laws with no common ground whatsoever.
The laws are different - Australia's politicians have actually legislated away the existence of women. Actually, worse than that, they've said that if you ever attempt to do anything for women, you have to admit men.
So the "women" category exists legally, but the law has no provision for actual women.
As I understand it, the point of aim of these cases is to demonstrate the state of the law, all the way up to showing that Australia is in breach of a bunch of international human rights conventions - ones that require them to have provision for actual women - thus forcing them to change them.
It's basically "reductio ad abusurdam" up the legal system - forcing higher and higher courts to actually look at higher and higher level implications of the law.