Deleting your data is absolutely a crime when you know the authorities could've wanted whatever it was you deleted -- even if they haven't told you yet. It stands to reason that providing a duress PIN that deletes your data when entered would be a crime as well, if said data is of interest.

Not to say that I personally agree with either of those cases. But what is considered crime can get pretty unfair when it comes to the authorities thinking you did something wrong.