I do believe the "Rough surface theory" applies as well in better/or greater amount of air flow.
Assuming that air and water have similar flow characteristics, I read (some time ago) that the Navy found out that after applying a "Shark skin" textured coating to the bottom of some of their faster vessels, that it required less H.P. to move them thru the water.
I also believe that's why Richard Petty once tried installing a vinyle top to one of his mid 60's Plymouth race cars. (Which was promptly ripped off) as soon as he reached "High Speed Oval Track Speeds".
But like Montana, until some body can come up with a way to apply a "textured" surface inside the NeedsWings intake plumbing. I'll go with the "smooth" is best theory.