Yes, I read Ted's post, and he was not correct. The photons do not "mix." There is no physical change to the photons. A red and a green photon do not run into each other and combine to become two yellow photons. Rather, red and green photons reaching the eye simultaneously are perceived by the brain as yellow. The only change to the combined spectrum past the color filters is whatever the filters filter out. The R,G, and B peaks are in the same place before and after the color filter. The photons that aren't filtered out just pass straight through unchanged. It's called "additive color" if you want to look it up.
Also, it's not the combined spectrum that determines how big the gamut is; it's the spectrum leaving each color filter. For example, you can have a very pure green from your QDs, but if your red peak is shifted too far towards blue, some red light will leak through the green filter making the spectrum from the green channel wider than the green primary from the green QD. That's exactly what is happening with the ~620nm red peak you see in the QMC picture. To get anywhere near Rec2020, at a minimum that peak would need to be ~645-650nm.
