Yep - all interesting questions after the event. Let's see what they say - maybe my info on the event is wrong too, but, as pilots, we need to understand that theoretically usable fuel isn't necessarily available.
I guess this is where fuel tank calibration helps, but significant blockages of fuel flow also need to be incorporated.
Perhaps fuel tank calibration needs be aligned with fuel flow. i.e. what comes from a fuel drain over X hours doesn't mean anything.