If an aircraft is known to have problems with Takeoff And/or Landing on the Aux Tanks, for example the climb/descent attitude causes the fuel lines to become uncovered, and the refueller has added the fuel that was meant to go to your Mains into your Aux instead so therefore the required fuel is now solely located in your Aux with your Mains being just about bone dry and you go to take off and have an engine failure due to the Mains being empty and the Aux being full, would the ATSB consider that Fuel Starvation because you had adequate fuel but just not in the selected tank or Fuel Exhaustion because the fuel you had in the Aux wouldn't have been useable for the Takeoff anyway?
In the PA31's case, the limitation in the flight manual that says DO NOT TAKE OFF WITH LESS THAN 1/4 FULL MAINS may be your undoing.
I've had refuellers remove fuel because the wrong aircraft (mine) was overfilled (oops, wrong Baron). Took two hours under the wing in 38 deg heat, but it was either that or be overweight.
As for checking x-feeds, what's wrong with getting into the habit of confirming your fuel (by PHYSICALLY confirming selector position) every time you line up?
Lights (strobes), Camera (xpdr), ACTION (fuel). Nothing like getting into good habits early.