It's true, encryption doesn't remove this ability. The reality is that the Constitution never provides this ability in the first place, and specifically prevents the government from passing any law that would provide this ability.
Refusing to testify against yourself (without a grant of immunity, anyway) is not a crime, it's your right.
I remember hearing about this being used as a justification by a judge in a case relating to encryption. It's just sad that most cases involving encryption / computer crimes are related to child porn charges so people are more worried about punishing the person than they are about protecting the rights of everyone that is brought into the court system.
So when they find a drive that passes the Chi^2 randomness test they know there has to be encrypted data on there, so you give them the key and they decrypt the outer ring (which contains nothing important). At that point they're stuck. They suspect there's got to be more to it, but they can't point to anything and say "decrypt this!", because there isn't anything to point to. So technically, they have to let you go. Or so I heard.