Interesting. So no matter what, it's impossible to get a "perfect exposure"? As in, there is only a perfect exposure for a shot, not a platonic idea of a perfect exposure for every color situation.
As the white husband of a brown wife, let me tell you, group selfies where I'm the only white guy in the picture invariably leave me washed out. Sometimes I make a point to expose for my face and everyone else darkens too much.
The problem is not only exposure, but how to fit the complete luminance range in the very limited emission range of a screen or a photograph after capture, and the answer is definitely "not linearly".