How would you prevent the token from being used by a different person than it was issued to? This is the online equivalent of getting your older cousin to buy you alcohol from the store using their own valid ID
I guess the practical answer is that it’s impossible because there’s always the option to have an adult perform the verification and then hand over the device to the minor
We already have penalties for adults mistreating children by exposing them to dangerous things, but this is orthogonal to age verification.