My guess is that GP means that it's not actually a competitive advantage, otherwise the markets would already be including women on their boards in equal propor

My guess is that GP means that it's not actually a competitive advantage, otherwise the markets would already be including women on their boards in equal proportions to men? Markets don't tend to experiment that much when they have something that works unless further competition shows up, see electric cars for example. Markets are meant to serve humans, not the other way around.