I don't think the GP implied that women must be the caregivers given that he himself would be happy as a stay-at-home dad. I think he was just commenting about a common scenario.

> If in a male/female relationship the female is the more ambitious one prioritize the male as the primary care giver

Why equate "ambition" with "desire for a high-paying career"? Somebody who wants to raise a family can also feel ambitious about it.