Kids can still just use a VPN to get around this, but at least it doesn’t compromise the security of adults.

And I can just sell my “you’re over 18” paper to some kid and he can use it. Spanish government proposed anonymous age verification certs some time ago. It’s also better solution than letting privet companies handle the verification but it doesn’t really solve anything. One leaked cert can be used by all the kids in Spain. If it’s truly anonymous you will never know who leaked it. If it’s not anonymous then… you know.