I always thought it was in case the pump circuit failed and the pump went into runaway-then the shut off signal closed the solenoid-S
good point, Although I have heard of ECU causing the pump to runway and the solenoid did not stop the fuel. But I always thought it was the AMA that came up with the
solenoid requirement. Also I think in some installs they can prevent turbine flooding if you forget to close the manual valve during refueling.