As a GM dealership technician I can say that is (somewhat) BS. Some (very few) cars have optional body accents, ground effects, spoilers, etc. that get installed at the dealership. The 2016 Corvette has "rocker panel moldings" "Front lower spoiler" and "rear spoiler" options that would be dealer installed. The rocker moldings do require drilling, but it looks like some of the holes are there from the factory, making fitment a factory issue, the dealership tech just finishes with the remaining holes.