Think of your radiator function is to heat the air passing over it. The hotter the radiator, the more it will heat the air. This heat comes from your engine. Therefore if the water in your radiator is hotter the effect will be a cooler engine.
Above argument debunks the myth of "give more time for the water to cool off in the radiator" to solve cooling issues.
I think this myth may have started when someone observed an engine running cooler with a thermostat than without and erroneously assumed that less water flow was the reason. More likely reason is the thermostat restriction created back pressure in the engine block which inhibited boiling, thereby increasing heat transfer and cooling system performance.
