The problem is that at that kind of pressure, you will have more hose failures, heater coil failures, water pump failure/leak, and possibly premature head gasket failures.
While the higher pressure will add many degrees before boiling point is reached, it doesn't keep the engine "as a whole" cooler, albiet there is something to be said for not flash boiling within the heads. In essense the higher pressure just raises the coolants boiling point.