That shouldn’t be. Could you show me ?
First, you should try to put the skin tones around the middle of the histogram, using the grey luminance at lower values. Filmic desaturates extreme luminances, “extreme” being what’s outside the latitude (outside the 2 nodes in the center of the graph). So that should fix part of the problem.
Then, if you use the chroma preservation mode, you will have to fix the saturation somewhere else (color balance). The thing is there is no reliable algorithm out there that can consistently remap the color saturation accordingly to the luminance correction. So my design choice has been to let users deal with it manually. The default color mode let the RGB values do their stuff, as would the base curve. The chroma preservation ensures the RGB ratios are conserved all along, but obviously, your eyes expect some sort of desaturation when the luminance is raised, and it’s not what happens here, so it looks over-saturated.
Also, the chroma preservation is not forgiving when your base picture has color casts and shifts, so, when your colors look off, fix the white balance first.