It’s quite simple, they would like to store photos without being able to see them, only knowing they’re not CP. If they scan on server, they need to be able to

It’s quite simple, they would like to store photos without being able to see them, only knowing they’re not CP. If they scan on server, they need to be able to see all photos, and eventually give them to any requesting authority. So the reasonable approach is to make clients that only upload photos that are not CP. The problem is that the implementation of that feels creepier than they anticipated.