The problem with that is, that prosecuters will then assume, that there still might by naughty stuff hidden. With hidden volume cryptography it's impossible to prove that one presented keys to the entirety of encrypted data.
From an information theory point of view, if each and every available bit was used it could be proven that the total entropy of the cleartext sums up to the total entropy of the ciphertext. In practice the amount of cleartext entropy will always be significantly lower than the entropy of the ciphertext.
From an information theory point of view, if each and every available bit was used it could be proven that the total entropy of the cleartext sums up to the total entropy of the ciphertext. In practice the amount of cleartext entropy will always be significantly lower than the entropy of the ciphertext.