They're basically, well not basically, they are a little box fan. Not even sure they still make them anymore. You know the 2ft x 2ft fans about 6in deep...Turn it on and put your hand in front of the intake side, then on the outlet/blowing side, take a guess which side is moving more air.

esc fans are designed to push air not pull it. It has to do with blade shape and pitch.

IDK of any esc that comes with the fan NOT blowing on the heat sink