Over the years, this has been tested more than once. I seem to recall the conclusion was as
@Challenger RTA suggests, the scoops are too low, within the turbulent slipstream along the surface for there to be any real passive benefit to opening those up.
We're talking about passive cooling and horsepower gains. It is our hope, opening those scoops allows air to passively flow inward to the engine compartment as the vehicle moves down the road, and carry heat energy away from the motor as this air passes over the engine, is heated, and flows downward and out of the compartment. Or, by pushing heated air around the engine away, and replacing it with cooler air from outside.
But tests have not shown there is any measurable cooling to opening those up.
Were fans put in place, or were there a sucking force at those openings, there may indeed be increased air flow.
The shaker hood setup benefits by openings about the same size as those of the rally hood (once opened). But the primary benefit is a sucking force pulling cooler (than within the engine compartment) into the engine. The shaker hood does not provide much (if any) cooling affect to the engine. But the cooler air helps the induction system make more horsepower.
It seems possible those rally hood scoop openings may let in some cool air at higher speeds - cooler air that may be sucked in by the air cleaner. But I don't believe it is as dramatic an increase in power as the shaker setup, because I don't believe anyone has ever been able to measure an increase in power between a rally hood with open versus closed hood scoops.