> Why not set up a government api where a site can get a yes/no answer about age using tokens, so the site itself gets no information but if the age is ok?

As I mentioned in yesterday's thread, an online API still allows the government to track and monitor residents, which is arguably worse. You no longer have plausible deniability when the government asks you to hand over your social media credentials because they now know that you have, or at least attempted to open, an account with that provider.

The better solution would be an offline, cryptographic "wallet" (similar to the EU Digital Identity Wallet) that only exposes the age information and nothing else, but I wouldn't get my hopes up.