I don't understand the point of the article, it seems to me that the point is that non compressed grayscale images don't take a third of the space of a compressed image? If we look at the last example the fist image 4:4:4 is 150KB the one in gray is 50KB (it seems exactly 1/3), the compressed images in-between take less space, but also the quality is much worse, I would say as expected. What am I missing?