somethings not right here

My experience has me believing that the cooling system has the easiest time keeping up at between 30 and maybe 45 mph. This is the speed zone where ram air is working, and the engine is not working hard, and the rpm is low.
As the car gains speed, the rpm is continually rising and so is the load. Wind resistance increases as the square of the speed. So doubling your speed from 30 to 60, requires four times the power, not to get there, but just to maintain that new speed. So going faster requires more power, and the transmission demands more rpm, and so more heat is being created, the faster you go.
At idle and stopped, is when the cooling system has the hardest time. It's all fan, so it better be able to do the job. This is why the shroud is so important.
But IMO, the factory 5 and 7-bladers have some pretty unique features. Those little wing-tips play a very important role.