Vettster,

I doubt the pump is tightly sealed against leakage into the turbine when you are filling the tank, so as Gonzolo said, this could prevent accidentally flooding the turbine. Also the ECU/FADEC driver switches (MOSFETs, I presume) are a potential failure mode. It would be possible for them to short closed so that the pump received full voltage. The ECU could not shut it off. In such a scenario, the solenoid acts as a redundant back up to let you save your plane.

Greg