Not sure why you are so adamant that color isn't leeching through the paint. It can happen if the paint being applied is not compatible with the plastic as it can dissolve some of the surface area and cause the colored plastic to bleed through the paint. I think you are assuming that they are claiming that the dye in the plastics is the only thing that is coming through, I would doubt that too, but I wouldn't doubt that some of the plastic along with the dye is melting and coming through the paint. Some paints are even designed to slightly melt the plastic they are sprayed on to create a better bond between the paint and the plastic being painted.
You remind me of my grandpa that swore up and down that a 35mm camera couldn't possibly have a mirror behind the lens because it would keep the light from hitting the film. He was raised when they had range finders and never kept up with technology... I suspect you haven't kept up with the different chemicals used in modern paints.
