Since I am assuming you got your information from the Technosquare article, and having put some more thought to it, I believe that the slotted openings were initially intended for a fan-assisted oil cooler assemble like this one:
Most likely there would have been more questions asked when journalists heard the unseen electrical fan kicking-in than just running it out in the open. I see no benefit in slotting the inner fender well cover for the grill opening mounted cooler as the radiator can help assist when they kick-on.