The minute black area on the inner part of the sector getting perceptually boosted with the same ramp width like the outer area is effectively how an outline on a shape would behave, not two shapes with no stroke width. I would expect the output brightness should scale with the volume/depth under a pixel in the 3d visualization.

Is this intentional? To me this is an opiniated (aka artistic preference) feature preserving method not the perfect one.

Btw the common visualization has a source and an author:

https://iquilezles.org/articles/distfunctions2d/ https://www.shadertoy.com/playlist/MXdSRf