So every corporation is liable for obstruction now for following their own data retention policies?
That depends on their policies. If they have competent legal counsel (and don't own/rent significant numbers of their own politicians) then those policies will not be only about what to delete when, but also what must be retained.
I'm not a lawyer, but your argument sounds like nobody should ever be able to delete any file, on any device, ever.
That's not how anything works either. If you have reason to believe it might be relevant to a court case, you're obligated to retain it. If you have no reason to believe it might be relevant, you're allowed to delete it. What can and can't be proven in court in between these things absolutely matters, but when it's obvious that something is pertinent, then you're obviously not allowed to delete it.
When a person is informed that the cops want to search their device, deleting information from it (including, obviously, tricking them into doing it) is obviously destroying evidence, so we're just having a fun conversation here which isn't relevant to the current discussion at all. It's very clear that what he did was destruction of evidence. I think it's approximately equally clear that he was being pretexted, but he still blundered and will still pay, and the only important takeaway lesson for anyone trying to learn something directly from this story is don't do that.
Yes, this is all terrible fuckery. Yes, in fact the laws are terrible too; making them less terrible wouldn't get someone out of this situation once they got into it, but it might keep them out of it to begin with. But wow, what a foolish thing to plan to do. And that's the problem with even having a device with a delete code — what's the legitimate use of a feature like that? To protect you from industrial espionage? How plausible a threat is that for you? Etc etc.