That does not factor the main point " that would not otherwise have become rationalist" There are loads of women out there on a certain road into rationalism. Those don't matter. By definition, they will become rationalists anyway.
There are large numbers who could, and we don't know how large, or how else they could, except HPMOR
Leaving aside gwern's rudeness, he is right - if MoR doesn't entice more women towards rationality than the average intervention, and your goal is to change the current gender imbalance among LW-rationalists, then MoR is not a good investment for your attention or time.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.