I saw the same thing when I was living in Port Elizabeth, ZA. It definitely works, the kombis with the best paint jobs always had more passengers.
However, like the article mentions, it was mainly a good indicator of someone who took care of the vehicle. That's the reason I preferred the decorative kombis... chances are there won't be any holes in the floor and a wheel won't fall off halfway through the ride. Not the case with some of the other vehicles.