Data encryption can be decoupled from key encryption. Let's say I hash the content of a file, encrypt the file with its own hash, and then encrypt the hash with the user's password.
This way you can have deduplication of data, and only an attacker that knows the content of the file can decrypt the file, but since they already have the file, it does not matter.
This way you can have deduplication of data, and only an attacker that knows the content of the file can decrypt the file, but since they already have the file, it does not matter.