Using the same logic, they could subpoena the grave that the body is buried in as the existence of such grave is a forgone conclusion (a shovel and dirt found in the car, a hole in the ground must exist) and thus would not be a testimony. The accused in that case is also a witness in that they witnessed the grave where the body rest. If they lead the police to a different hole then analyze of the dirt can prove contempt of the court.

The rule make very little sense. I would not bet in favor of it continuing for long. The whole idea that the prosecutor is only asking for the container and not the content was extremity transparent to begin with, and judges who have rejected that argument have said just that. In that case the conclusion the judges made is that a request for the container (ie the unencrypted device) is the same as a request for the information itself, and thus should be seen as such.