The problem is that the temperature you feel on your hand is not necessarily the temperature the chip is operating under. If your hand is warm that, ironically, means the heat is dissipating effectively. If it's not dissipating, then your hand will remain cool because all the heat is still on the chip.
So unless Apple gives you a way to read the chip's own temperature sensor data, what you feel holding it isn't that useful. (From a performance standpoint at least. Having a handwarmer when you didn't want a handwarmer is a different kind of problem.)