You're mixing up false positives and false negatives. Nobody is going to be incorrectly blocked under this system unless they lost their ID, and the fix there is getting a new ID.

Some kids skipping the block sometimes isn't catastrophic, especially because there won't be all this peer pressure to join adult social media when 90% or more are blocked.

You know this? My guess is that companies will be held responsible for anyone accessing there content that is not supposed to. In that light they will feel the need to block any unknowns that come through rather than potentially face issues if someone who is technically banned from accessing gets in.

I'm not sure how you confidently can say that every company is going to allow the people we can't verify have access?