Exactly, a high flow pump will not move the water thru the radiator too fast to be cooled. That is folk lore. Thermodynamics tells us that if it moves thru the radiator twice as fast as a normal pump, then any given unit of water will get back to the radiator twice as fast so it will be cooled in half the time...so it all comes out to the same answer. Normally, it should cool even better because the higher velocity of the water flow thru the tubes causes more turbulence in them and that aids in heat transfer.
A big advantage of a high flow pump is that it will build higher pressure in the engine which promotes more even cooling as well as raises the boiling point against hot spots internal to the water passages. Pressure in the block is higher than the pressure in the radiator which raises the internal boiling point. When using a high flow thermostat, a high volume pump should be used in order to maintain this pressure.
In some cases, in vertical tube radiators, the cap can blow open because there is higher pressure in the radiator tanks than the cap is rated for. That is the advantage of horizontal core radiators...the cap is on the low side of the pressure.