The site is pretty dreadful in the information it provides. For instance, the "one in ten people" getting endometriosis is created by replacing 'women' with 'people' which, of course, should not be done without halving the number, given that half of all people are male and the rate of endometriosis among male people is so low that it won't affect the result.
So it should be "one in twenty people", but of course that reduces the level of information from "one in ten women".
And if you had to pick just one variable for predicting the group most likely to suffer from endometriosis it would be being female. But this site argues that it is not a useful variable at all!
The site has a long quasi-scientific argument that sex is not a relevant variable at all (!), given that all the different ways of defining sex don't classify every single person into either male or female sex in exactly the same way (though they are all going to classify the vast, vast majority into those two sexes the same way).
This is like saying that the concepts of light and dark during a 24-hour cycle are not useful because we may have trouble defining exactly when dawn begins or exactly when dusk begins and what exact level of light or darkness would move us form light to dark or back. That this is true does NOT mean that the concepts themselves are without value.
The site also clearly prioritises trans men and female nonbinary individuals, even though they are extremely few compared to the number of female women. And it erases the female sex from language, thus contributing to patriarchy by making it ever harder for the more oppressed sex to organise politically around the issues which matter to it, including endometriosis.
It is not a pleasant feeling to be erased.