Things are often classified because of how we know the cat died, not because the cat was special. Suppose you've recruited a foreign intelligence officer to work for you and he happens to mention the cat dying during a debriefing. You can't just declassify the unimportant bits because enough of them will tell you who said it.
It's the same problem as FAANG collecting mountains of "anonymous" metrics. Pretty soon, you can determine who the "anonymous" user is.
I think everyone knows we are in Afghanistan and the cat was a stray on our base. But you’re right. Maybe the fact that Nothing Happened was what was classified, not the cat? Who knows.
