You see no difference between sitting 0.5 meters away from a screen that's projecting its own light or sitting 15 meters away from a screen that has light projected onto it?
A photon is a photon, regardless of whether it's emitted directly or reflected. All that matters is vibration frequency and intensity of the stream of photons.
Do you disagree?
Maybe kungtotte is talking about accommodation or vergence, though I don't see how these are relevant to f.lux or colour temperature.