Sorry I should have been more explicit. I've seen all sorts of dumb shit in NDAs. What I meant to say was I've never seen that kind of language in an NDA drafted by a decent lawyer that expected it to be enforceable.
Competent legal council would have the whole thing invalidated because you cannot mount a legal defense to a document you can't acknowledge the existence of in open court. Judges only let that stuff fly when you risk human life or judicial process, not in civil cases.
Maybe it's to guard against the possibility of revealing what's covered by an NDA by answering yes or no to increasingly-detailed questions about what is and isn't covered by the NDA?
