I've seen this a lot in the US, and at least in the North East, it seems like a lot of companies are moving away from this model. It's a really difficult policy to even enforce without being discriminatory against men.
At this point in my career I take it as a red flag against the company. Women obviously still face many more hurdles than men when it comes to workplaces and an expanding family, and both genders deserve more paid time off in the US when the family grows, but policies like this end up specifically targeting men more often than not.
By default it defines men to be a less important care-giver than women.
I generally agree. I'm not especially interested in litigating which gender is worse-affected since you can spin it either way (e.g., "By default it defines women to be less important employees"). Suffice it to say it's more restrictive to men than to women (i.e., men don't have the option to take longer leave if they wanted to); however, there may be second order effects that are harmful to women (a firm that discriminates like this may be less likely to hire women because they would de facto be more likely to take off longer). In any case, it's all wild speculation.
At this point in my career I take it as a red flag against the company. Women obviously still face many more hurdles than men when it comes to workplaces and an expanding family, and both genders deserve more paid time off in the US when the family grows, but policies like this end up specifically targeting men more often than not.
By default it defines men to be a less important care-giver than women.