Well obviously when you put it like that, there is no rationale behind it.
Because like a lot of the other assertions, it's all smoke and mirrors. When you actually untangle it, there can be no rationale. Why should you have to share anything with people who feel 'feminine' or feel 'masculine'.
For bathing, or going to the toilet, or being punished for a crime?
Because it's not about that. It's about men who want to be treated in a certain way.
This holds true for both those with gender dysphoria and those with AGP. And it's why feminists recognise the inherent misogyny/sexism which underpins the lot.
For men with AGP, it's fairly self explanatory. It's arousing to be treated as a 'woman'. But only 'their version'. Im fact most of them will be quite upfront about it.
And I believe it holds true for men with gender dysphoria, too.
I believe they perceive women in a certain light. Possibly on a pedestal, possibly delicate, gentle, nurturing, softer, more empathetic, etc. And their rejection of everything 'male', becomes more understandable.
This is the way they want to, not just present, but be accepted as. In other words, treated as. It's still an idealised version.
(I wonder if continues to come down to the Madonna/whore scenario?)
So to answer your question, I believe they want to be categorised on that basis, so that they can be treated on that basis.
It's less about how they genuinely think or feel, and more about external treatment, or, in other words validation.
The fact that it's regressive for women, doesn't matter.