New "wage gap"

People seem to be coming up with more and more new, creative and inventive ways to stigmatize men and corporations, and put the dead-old gender wage gap issue on the news.
It’s interesting to see in this article how Neandelthaal men actually out-earn egalitarian tree-hugging type male in the workplace. Forget all the circular and self-serving reasonings for this wage gap between traditional and egalitarian males that these scientists tried to come up with to cozy up to power-feminist type; may be one of the reason for this is that egalitarian male put brake on themselves - they might be thinking, “if I perform at my full potential, I would be so far ahead of women in the next performance review and that is so against my egalitarian view; I will perform on a par or below my female colleagues so that women will be promoted ahead of me, get higher wage, and I can show with my own example that women can be as good as men, or men can be as bad or even worse than women”.

Or the other reason would simply be that these egalitarian men are simply not as good as traditional men. Even if you control for IQ or education, you cannot control for their ability or performance; it may not simply be that these testosterone-ridden traditional males were aggressive during salary negotiations only, they may have been aggressive in their work also, aggressive in completing the task, achieving goals, etc., and these may have led to higher performance review, hence faster promotion and higher salaries. On women’s side, whether they have traditional or progressive views on gender roles would have little to do with their testosterone level (which is low across the board), and therefore resulted in little difference in wage-gap=performance gap between them.

Why do you have to assume that men (or women) with similar IQ or similar education, background will have identical performance?