The difference is the attack surface. They only get one chance to plant drugs. They have unlimited attempts to fake finding data on your encrypted drive image.

The difference is the attack surface. They only get one chance to plant drugs. They have unlimited attempts to fake finding data on your encrypted drive image. "Your Honor, the new version of the program found kiddyporn that we missed before." And even if you decrypted the drive you wouldn't be able to prove you didn't have the data steganographically hidden, so there's no possible way you could refute the claim.