That's a possibility, for sure, but the cowl "louvers" (openings) sitsright at the base of the windshield. I'm not sure how it works, but I have read many times, that the base of the windshield is a high pressure area if the car is going very fast, and as such, air that exists there, would be trying to push its way into the holes in the cowl, and the underhood air would stay right where it was... under the hood.
