I don't see any promise there that they won't somehow store your encryption key in a place where they can access it. I see a huge line saying "we invite you to

I don't see any promise there that they won't somehow store your encryption key in a place where they can access it. I see a huge line saying "we invite you to try and catch us and if so we will try to find another way that you haven't yet found out about". So I think you failed on your premise.