As I cannot give you an exact answer, I will try to suggest a few points. Let me try to respond to some of your queries. Not an accurate usage for sure. I have two videos on Agent Orange, and one of the directors distinguishes the two by calling one 'khoa hoc' and the other 'tai lieu'. I hope that the above might be of some reference to you, Diane.
All thoughts welcome.
You can see an illustration, literally, of this attitude each week in editorial cartoons in the Vietnamese-language press outside of Viet Nam. There are wonderfully funny stories along this theme from the camps. Well, the stories are dreadful,actually, because they are usually told of some man who met a sad end. But they are told in the spirit of humor and I honor that. The stories are told by the people who had the good sense to keep their mouths shut, while a prouder comrade confronted the organized ignorance of the guards.