I think this has been a thing since D1 and still blues are overwriting prime, exotic, shards, prisms, etc. You need to do that or make the postmaster full message well before its actually full. Since several people have an issue understanding some of us don't run normal anything. I'm not using the PM for storage. I've masterworked and shaped everything I can. And the vault does not allow you to store shards. It's thar simple.