Batch and sequentially injected engines produce the more or less same power for the same size injector. I say more or less because you shouldn't run injectors at dutycycles greater than typically 80 - 85% and this is where sequentially injected engines can have the edge over batch fired if the injector rail is too small. This is because you get greater pressure fluctuations that reduce flow on the batch fired system.

Those quotes are misleading because most sequential Ford ecu's start their injection when the inlet valve is closed, so being limited to when the valve is open does not apply. At higher pulsewidths the injectors remain firing until the valve is open.