Visually, the result looks a lot more pleasing to me, in any case. The perceptual gamut mapping libplacebo does will never produce perfectly shaped vectorscopes, so the goal so far was to remove spikes and other odd shapes with increased precision, and work on the visual result.
I'll be updating MC with a new version of libplacebo this week, and also add a few new options that might help low-brightness/low-contrast cases like projectors, as setting the nits below the reference value is not really recommended. Not sure yet what I should do with that option at all, maybe shrink it and properly explain that it's not the same as madVR's setting.