I mean it makes perfect sense right, I thought this was basic economics.

Market dictates to maximize shareholder value you need optimal board members x,y,z. A law like this makes you replace z with e.

It's not that a woman can't do the job, but instead that the supply of women capable is much lower. As a result, with a shortage and a mandate for women board members some companies will get sub-optimal picks which result in sub-optimal results.