Seems this case isn't so much about what the police can do in the interrogation room, as what evidence is admissible in court. It's quite easy to enforce the provision that they can't tell juries you refused to hand over a password.

That's a moot point if you do reveal your password, but coercion is a separate issue we could try to address, which would be pointless to address if they could get you convicted simply because you refused.