> This assumes all men would be equally likely to get to have sex with the women.
I think the OP meant since no one was expected to be monogamous, there is no "cheating" and no conflicts of "infidelity". More women having multiple partners means potentially more different men would be having sex.
> it just means many men working for free (like drones) to support other men's children.
Well, not just anyone's children, because they would all be related by blood. They'd be taking care of family.