For example, if there is a small error in the green channel that cannot be represented, and another small error in the red channel in the same case, the properly weighted sum of these two errors may be used to adjust a perceptible lightness error, that can be represented in a balanced way between all three color channels (according to their respective statistical contribution to the lightness), even if this produces a larger error for the hue when converting the green channel.
This concept illustrates how minor mistakes in the green and red channels can be combined to adjust a perceivable lightness error, which can be fairly represented across all three color channels (based on their statistical contribution to brightness), even if this results in a greater error for hue when converting from the green channel.