I agree 100% with you sonoronos.

Im fairly certain that the heat being exerted on the pistons is fully from the combustion process. If the oil in any way contributed to extra heat on the pistons it would be such a negligable amount that it's not even worth worrying about.

The purpose of oil coolers in high-performance engines is to help get a longer life out of the oil, and in no way helps to "cool" the engine any further than reducing friction.