G0ULI,
Quote ..."My interpretation ......... The shed load switch was found still in its normal position, so the drain on the battery would have been significant with apparent attempts being made to restart an engine."
If restarts were being attempted the Engine main switches would not be in the Guarded Flight positions unless both restarts had been successfull.
You do make good points about the fuel system, and the fact that the transfer and prime pump switches are all the same and in a line above the pilots head does make it very possible a pilot could select the wrong pair if not monitoring the caution panel for correct operation, particularly at night.