As a counter, actual age verification is being rolled out in other places. I really don't think we're in a position of choosing between no age-based access mechanism, and age-based access mechanism. Between the anti-porn types and public demand for some kind of regulations on social media, regulation of some kind is inevitable.
Our actual choice may only be what type of restriction we can live with, and I much prefer this type to the kind that requires websites to demand my id and photos of my face. Especially since some implementations of this concept (the California one, I think) declare that websites aren't legally required to look deeper than the attested age, which is a very nice feature.
Mind you, I don't know why the legislators are bothering mandating OS support for these features. It would be much easier to mandate that websites support the feature, make it clear to them that supporting the feature appropriately will free them from liability for children accessing content, and then wait as users demand that their OS support the feature.