"I really struggle to identify the difference between a woman discounting the opinion and lived experience of a man because he is a man and a man discounting the opinion and lived experience of a woman because she is a woman".
the critical difference is that these are not symmetrical situations.
Men know less, from fewer angles, about what life is like for women, than the other way around.
No woman can know exactly what it is like to be a man, but they do know a lot about men's views, expectations, ways of thinking and being, etc, because men operate in the world on the basis that the women should fit in with them.
Women do not operate in this way, or have as many opportunities to educate men about what they are thinking, feeling or doing - partly because men ignore women when they try to communicate with them. They are able to do this because it poses little real real risk to them. On the contrary, women who ignore men's attitudes are at material and physical risk every day.
So when a man says "speaking as a man, I think [you're making a big fuss about nothing] [housework is not important] [you probably do deserve less money than the men in your office as you are probably not working as long hours]" - I don't want to hear it. I know men think these things. They're wrong, and I have little respect for them, and I'm bored of them. I am interested in what women think.
On the other hand - if a man says "I should clarify before posting that I am a man" - that doesn't bother me at all, if it feels like he just doesn't want to post under false pretences.