I could be wrong, but I think the parent comment is just a reference to the fact that brown doesn't exist. There's no wavelength that our brains map to brown. Instead what we perceive as brown is just orange, but less bright. And wether we see it as brown or dark orange depends entirely on context.
Colors isn’t the same as wavelengths, though. Two different colors having the same wavelength isn’t a contradiction. Similarly, different wavelength mixes can constitute the same color, because the human eye only has three color receptors.
