usually the pumps inlet is mid tankish. either way, im agree with you as once the fuel is below the pump inlet, its no longer gravity fed.
its really a mute point for the fass, airdog, and fuel lab. they have no issues under a draw situation. the Kennedy's and other fuel pumps like it (holley and so on) CAN have issues drawing "uphill" so to speak as they are not really designed for it.
the only time i worry about a sump, pump design and line routing is in a race application. You have much more freedom to setup the system to work 100% correct since your constraints change IE: could use a different chassis, fuel tank/cell, pump location, line location, no bed, and so on.
again, this "benefit" is extremely minor since the fass, airdog, and fuel lab all have the ability to use the stock pick up (no cutting or dropping of the tank) and will supply enough fuel for 1k hp.