Age verification inherently requires identity verification.
The UK's Online Safety Act originally had a proposal that would allow users to purchase an ID code anonymously in cash from a corner store, presenting only ID to the cashier the same way as buying alcohol. This was never implemented, because it's more useful for the government and corporations to link all online usage to a government ID.
I didn't know the Online Safety Act had this proposal. Do you have a source?
I've been proposing the same thing on this site for months. IMO anonymous age verification with no record-keeping is the only form of age verification that should exist. No zero knowledge proofs, no centralized government identity provider, nothing.