I've always thought it was stupid that we have a stigma about boys getting dolls, yet have progressed to the point where we expect men to dote on and care for their babies. When "dolls are for girls" was first conceptualized, the basic idea was that the only interaction men would have with their kids was disciplining them. It makes zero sense to have a boys-dolls stigma now.
Regarding children, they are learning about and being schooled by gender differences long before anyone verbally tells them "dolls are for girls, cars are for boys". Young children are absolute sponges, soaking up information based on their observations.