The key point is that there has to be a slow vertical panning happening as actual content. If that happens, then the on-disk representation of a color channel can end up physically below/above what happens before/after in the movie, drawing out the "actual content". This is why end credits were the most likely visible artifacts.

One other important aspect is that by changing the angle of lighting, he could basically filter out data at a relevant wavelength.

--

At least that's what I got from the video.