In a sense.  Gray is defined (in any given image) by R=G=B so when the red, green, and blue values are equal, the color is considered neutral and your curves for the "Neutral" channel will be applied.  As the RGB values start deviating from neutral, the curves for other channels will start blending in.  For example, for color 128,128,128, it will use solely your curves defined when "Apply to" is set to "Neutral".  If another color is 135,128,128 (slight red tint), it will be weighted so mostly the "Neutral" curve is applied but it will blend in some of the "Red" curve as well.  And of course, if the original color is 128,0,0 (purely red), only the "Red" curve is applied.  This gives blended coverage and avoids posterization between hues.

Regards,
Mike