Think you'll find that the cars used (like in the film strips, some early ads and so on) are the preproduction and late styling cars and can often have a number of not RPO details
Over the years have seen a few cars at shows with the dealer rear tow package. Most of the time it was on one of those you see where the owner loaded up the car to stand out. Sure many of us have also found the evidence of the hitch - holes drilled and not always patched in the body, bumper and so on depending on the style