Agreed, WorkingSection.
If it was upside down, nose down, then almost all of any fuel in the supply tanks could have drained out into the main tank, but that's not what happened.
If it was upright, but steeply tail down, then a lot of the main tank contents could have made it into the supply tanks.
In particular, if is was inclined, and tail down, then the lower supply tank could have filled substantially.
Either one of those scenarios would, I think, have substantially complicated the job for the investigators.
The information that the AAIB have and reported about the fuel levels in the tanks could easily have been compromised if the wreckage had come to rest in a different orientation.