Humans see more than 8-bit RGB. Humans can see light polarization and stereo disparity, but more importantly we can interact with things we look at. XYZ is the

Humans see more than 8-bit RGB. Humans can see light polarization and stereo disparity, but more importantly we can interact with things we look at. XYZ is the "most optimal" 3-channel colorspace but it's a simple transformation from RGB, so it doesn't matter - the model can learn it if it wants to.