If diverse companies perform better, this would surely mean that there is some sort of difference between the sexes? How else could diversity have an impact on the bottom line of a company?
Well, if women really make 87% of what men make for the same work (or whatever the latest number is), it could save the company 13% or more on car insur- I mean, labor costs.
If it is really true that women make 87% of men for the same work, any company that is driven by profit would exclusively hire women. The alternative would be that sexism is so rampant that it trumps profit driven motivation, am I missing something, or is that what you are suggesting?
I'm not really suggesting anything other than that, it's a hypothetical explanation that disproves the notion, "if diverse companies do better, it MUST be because of differences in the sexes". Admittedly not a high-effort comment.
In answer to the rest of your comment, it's anybody's guess and nobody agrees why. Maybe the stat is wrong, maybe the sexism is just that rampant, maybe the women-only candidate pool is inadequate (small), maybe there is a performance difference, etc.