> If it becomes commonplace, the iPhone could vouch for you about your age, without disclosing your identity.

No, it really couldn't. If it can't disclose your identity, then there's no mechanism to revoke a compromised or cloned identifier, and no ability to demonstrate in court that you performed the necessary diligence correctly.

Age verification systems must, inherently, either produce a secure proof of age with no genuine anonymity, or a chocolate teapot highly insecure proof of age that's no better than a "I am over 18" tickbox that isn't going to protect websites in court from these clumsy laws.

Eh, companies would probably be permitted to keep using the systems since "it's the industry standard, there's nothing more we could've done", and it would just become another instance of regulatory capture.

See, e.g., the GDPR, which as written has strong language against storing data, but as applied is riddled with 'reasonable' exceptions that have never been tested in court. It's like Schrödinger's regulation, it's both incredibly restrictive and trivial to comply with (unless you're Super Evil™) at the same time, somehow.

> no better than a "I am over 18" tickbox

Surely even a flag locked behind the "parental controls" section of an iPhone is much better than a tickbox.