I am asking if pilots are aware, as general knowledge, that a significant amount of fuel is unusable in the main, if the transfer pumps are not working.
Possibly, possibly not. I don't remember it being mentioned on our ground school. Certainly the FLM makes no mention of unusable fuel after a double Transfer Pump failure: only Single Pump failures. It was only after I flew with the Transfer Pumps off, to see what would happen, that we knew that as much as 255kgs would be unusable in the main tank.