No… i don’t think that is the case… The motor is probably either voltage regulated or current regulated… it would be poor engineering to allow the motor to just free spin to infinity under no load… actually… it would be utter stupidity.
Actually the pump would be voltage regulated because it’s power comes from the +12V battery lead… also … DC motors draw their highest current at stall… so no load = less stress on an electric motor.
The only thing you don’t want to do is run the pump without fuel because the fuel acts as a coolant of sorts… without it you could overheat the fuel pump.