Q.G. is probably telling us that the spectrum of light visible to human beings is composed of many more colours than the three, RGB, fundamental colours of additive synthesis. Something like yellow light exists, or orange light for that matter.
If I get it right, Q.G. is saying that even if it is technologically feasible to make yellow light as a superimposition of red light and green light, "yellow" light exists in nature independently from red and green. Or to put it in another way, the three colour theory is something that works in practice, but it is not the way things are "in nature". "In nature" there is a certain portion of the white spectrum that we humans perceive as yellow because it is of a certain wavelength and not because it is the result of the superimposition of blue and green light.
Yes, and what Q.G. does not understand is that no one disagrees with that. He somehow takes the explanation of additive color theory as applied to photo materials as a contradiction, which it is not. Both are true and can be demonstrated.
I do use a digital device in my photographic pursuits when necessary.
When someone rags on me for using film, I use a middle digit, upraised.