DxO calls it the luminance or luma curve. Luminosity is a different beast, but related.
Luminance is a weighted value that takes human vision into account. Luminosity doesn’t do that and (our perception of) colours can shift due to such differences.
Above, we see the results of pulling the “white point” towards the center of the tone curve’s scope, once for the RGB curve and once for the LUMA curve.
Depending on how each RGB triplet travels in 3D, perceived colours can change in the planes perpendicular to the black-white axis. → sRGB in 3D
Please note that the differences are less visible in well exposed images that have a histogram curve centered around its middle.