Thing is though, this and stuff like "hand over the keys to that encrypted data" are really easy ways of getting just about everyone into prison.

I could for example argue that you, by changing the profile picture on your blog, have used a warrant canary too. Do you have any way of proving that you didn't? You certainly can't argue that you don't need one (this would imply you haven't receive a NSL which would be a warrant canary statement in itself), you can still argue that you haven't used your profile picture as one, but then we're back to square one, with them saying "You have!"

If the government wants you in prison, they'll find a way.