Some will, but when you are fighting to change norms language and optics are an important part of that. I think the movement would have been stronger had it avoided language implying gender essentialism.

But yesallmen/believeallwomen DID, as you say, come with widely available explanation and purpose.

...and you don't think that choice of language played a part in the reaction to things like when Jimmy Bennett accused Asia Argento of statutory rape and she paid him off to shut him up? I mean, she more or less literally did what #metoo was accusing powerful men of doing, had done it recently at that point, and didn't get half the shit most #metoo targets got as a consequence. Or that aide that accused a CA legislator of being inappropriate with him, so she investigated herself and found no wrongdoing on her part.

And even the people who claim to be all about #metoo and #believewomen get...picky about that when a woman accuses the wrong person - see Tara Reade's accusation against Biden.

It absolutely did not. It came with shouting down anyone who wanted to question women who came forward with rape accusations. That's how some of these highly-publicised cases, like Matress Girl, resulted in immediate expulsion of those accused. Had they done actual investigating into the matter, they would have seen the woman absolutely should not be believed, but that went against the slogan.