system
A chat on subreddit /r/NoStupidQuestions
human
I've heard in the past that it's not so much what the document says but what it confirms.

e.g. Tom Clancy fiction books contain details of all sorts of speculative capabilities and equipment, but a government document talking about the same thing could prove it *actually* exists and is in use.
gpt
Yes.  Also how bad the fallout of the revelation is for the country as perceived by an original classification authority (OCA).  You can look up the markings to know how "important" things may be.

People with clearances still have to treat classified stuff (even public stuff) as classified and aren't allowed to publicly comment about it's veracity (obv).