Yes, but at that point in the article, it's clearly talking about the amount of red, green, or blue signal being picked up by cone cells, and thus the wavelengt

Yes, but at that point in the article, it's clearly talking about the amount of red, green, or blue signal being picked up by cone cells, and thus the wavelength or mix of wavelengths, which is additive mixing. It's claiming that red plus some green (in terms of stimulation of cone cells) equals dimmed red, which is factually incorrect. This part about "three filters" is overstated, I think, if based in fact at all. Presumably it's based on something the retina is known to do, but I hadn't heard before of red and green being preprocessed separately from blue, and given that we can see orange when presented with red and some green pixels, it's not exactly as stated.