> and the policies need to be designed such that the woman has to be back at work for at least some of the paternity leave, it can't all be used concurrently.

Not sure how to apply a legal framework, but in my area this is often enforced by the lack of daycare options for <2yos (the threshold might be lower, but about that much).

Very rare to see parents around me take their parental leave at the same time bc they'd be risking still being on a waitlist when they're done.