Disagree: it's a terrible question. The answer (all of them) is something you either see or don't, and neither tells you much more than one bit of information about the candidate.
I'm not convinced; it at least tells you if the interviewee will rush to an answer that appears correct and say "All of them", or if they'll consider it a little more carefully and say "The rest of them". Or if they'll ask for a strict definition of what it means to pass a chair on the way up, to clarify whether or not you count the chair that you're riding on as one that you pass.
