If you take as a given that consenting adults should have access to sexually explicit material generated by other consenting adults; the potential for harm to adults is huge with the current implementations.
Can't wait for the headlines when the entire watch history of some famous person is released after someone recognises them in their "age verification scan".
It's about the only good thing which could come out of digital ID. Being able to proved proof of age in a double blind way.
How would that work? do you want to provide government id to watch porn?
And how is this helping since it's not going to work overall (other sites, torrents, etc)