Since pixel colors "overlap" in a way due to cross-talk, does this mean that colors regress towards the mean (which is why this image looks saturated)?
I don't fully understand what you mean by regress towards the mean, but I can share the way that I thought of the color desaturation result. Saturation refers to the purity of a single color. When purity is low (desaturated) the resulting hue is grey or black. When purity is high (saturated) the color is brilliant, intense, and you can't identify any other color within the color. Since cross-talk is happening in this image, purity is low, and the image is dominated by shades of grey (since grey/black is what you get from mixing many different colors together).