wow, you need to talk to some engineers. I will have to brace you for the fact that they may laugh at you. the heat sink is not the external case. the heat sink is within the Surface Pro. It still comes out vents
your knowledge is pretty ridiculous. you really do need to take a thermodynamics class.
Okay, if you put a hot metal pot of boiling water in a cardboard box and leave the top of the box and the pot open. The cardboard box will get warm. That doesn't mean the proportion of heat that is dissipated or transferred is appreciative. Of course, any device will get warm and that means heat is transferring to the material. But that is not what is really cooling the system down.