Coated paper versus uncoated - why the difference in color??

Everyone who has been around printing for a while knows that you can get richer colors on a coated stock than on an uncoated stock. Ask anyone who runs a press and they will (likely) say that it has to do with "holdout". The uncoated stock soaks up the ink so that much of it gets hidden behind paper fibers, whereas the ink sits on top of the coated stock. I have a different explanation, and I back it up with the experiments in this video. (This was my presentation from the Technical Association of the Graphic Arts virtual conference in 2021.)