The only thing you can take out from this study is that men staring at a women's breasts will affect her performance - at maths, but possibly also in salary negociations, in meetings, interviews etc.
THe conclusion that men are immune certainly is invalid, they would have to find something that is culturally as uncomfortably objectifying to men as staring at breasts is to women. And that is harder to find because our culture doesnt objectify men on obviously visible things the way it does women.
So it is a disadvantage women have - one of many that act cumulatively - one that wont vanish overnight because it needs the culture to change, and that takes a couple generations, each one having grown with less toxic messages and therefore less affected...