I was not aware of this spec but it looks similar to what I've written for blossom in that it uses the sha256 for the id of the file. however I think it has some issues 1. Its only focused on images and videos. if we want to solve the storage problem it needs to be generic 2. It relies on the "/.well-known/nostr.json" document for servers to describe themselves. this makes servers not interchangeable when it comes to retrieving files 3. It only focuses on uploading and retrieving the files. I think its also necessary for users to be able to list and delete the files they have on servers