The aero bits you are referring to do not meaningfully contribute to aero performance in any downforce way, but they do shave off a few counts of drag, which helps the fuel mileage rating just that little bit. They’re not really attractive, and can scrape themselves to bits, especially if you’ve lowered ride height on your car or have a steep driveway entrance.
The other comment (I’m sure in reference to early 2013MY) was also correct, that Conner Ave did ship some early cars without rear brake duct nozzles. There was a shortage of those parts, and also some question about how effective/necessary they really were, as it was believed that the positive pressure coming from the bodyside scoop would pressurize the rear wheel opening and help push the hot air out… but that was never actually tested or known. In fairness, I recall that Engineering agreed to let Conner ship those cars shy those end fittings ‘as is’.