Every one of these age assurance laws basically says:

1. The OS vendor must provide an age bucket using the minimum amount of data necessary

2. App vendors (i.e. Facebook) must use the OS vendor's age buckets to determine age

The idea is that the next time Facebook gets hit with a child endangerment lawsuit, they can say "Well, we used the age buckets the government told us to, and they said the plaintiff was 18+, so we're not liable".

This, of course, assumes that most social media and Internet regulation will continue being targeted at children only, both because courts are reluctant to enforce 1A on laws that censor children[0] and because the current political class actually benefits from the harms Facebook does to adults. Like, a good chunk of government surveillance is just buying data from Google and Facebook.

[0] The root password to the US constitution is "th1nk0fth3cHIldren!!1" after all