Thought experiment: What if you kept two sets of bank records for your business. One set of bank records were truthful and demonstrated your guilt. The others were falsified and demonstrated your innocence.
What would happen if, after your bank records were subpoenaed, you hand over the falsified records?
Well, you'd be committing a crime. Maybe you get away with it, or maybe law enforcement figures it out and you get caught. Depends on how clever of a criminal you are.
Same thing here with your double-plaintext encryption.
Hmm... I believe there may be a distinction here. Decrypting to the false virtual contents would be more like presenting a copy of the bank records that were correct, but the file had been corrupted and the data was unusable. However, the corrupted but true records had been created before the subpoena (not trying to obstruct) and were handed over in good faith.
You wanted the contents of this drive? Here they are!
The owner of the drive is definitely in a legal and moral grey area, but it would be supremely difficult to prove mens rea in this case.
Interesting thought experiment: What happens when someone fills a hard drive with junk data and then encrypts it, then gets subpoena'd for the unencrypted contents of the drive?
The scenario you describe is not at all like the situation at hand. Data corruption and encryption are not the same thing as encryption is a fully reversible process.
Further, the owner of the drive is not in a legal or moral grey area. They are in a "black" area where it's quite clear that they are being intentionally deceptive in defiance of a court order.
What would happen if, after your bank records were subpoenaed, you hand over the falsified records?
Well, you'd be committing a crime. Maybe you get away with it, or maybe law enforcement figures it out and you get caught. Depends on how clever of a criminal you are.
Same thing here with your double-plaintext encryption.