The MAGA Documents were "super" top-secret

Media is reporting that some of the documents in Trump's possession were so highly top-secret that only a handful of people in all of America have the clearance to view them. I thought to myself that this is not too surprising. There's information so sensitive that only a handful of people are "cleared" for it. Nothing new here.

But then they went on to say that the government cannot even describe the documents because they're too sensitive. This means that even divulging the topic of the documents would harm national security (in their estimation).

So I came here for the wisdom of Politalk. Can you provide me an example of a document so secret that it cannot even be vaguely described? Our SIGINT stuff the NSA does is highly classified but it is no secret that we do SIGINT. Spy satellite technology is super classified, but it's no secret that we have satellites in orbit. And then you have various military tech projects, but I see no reason that if the documents were military related that this fact cannot be stated. And, finally, you have the CIA with their human assets (HUMINT). They keep names of spies closely guarded, but if the documents were related to human assets, I see no reason this could not be said (without releasing names, of course).

Seriously, what kind of "topic" is so sensitive that the topic itself cannot even be described?