IF it is/was any kind of a problem, don't you think the problem likely would have shown up somewhere on one of these MANY truck camper forums? Through the decades (6?) the Alaskan Camper has been mated to most of the different truck body styles/models/brands, all with somewhat different aerodynamic characteristics, likely a few driven at fairly foolish high speeds, diven by all kinds of interesting people, and some drivers likely are sensitive to loud noise or radical air currents.....
My new-to-me Northen Lite is up in the air 11'3" (including the air conditioner). I would think if that big camper, with its huge bow wave of air, doesn't cause an issue, how likely is it for a foot-and-a half-or-so height above the cab to cause a problem, even if it sticks out beyond the windshield a ways..... As do MANY brands/kinds of truck campers, especially on standard cab pickups.
I'd tell your friend to relax about his concerns.....