PaQ WaK
It is possible my input is irrelevant tho and that I don't exactly understand your concern.
My concern is that it looks wrong and not pleasing. And I guess it looks wrong because in real life the shading would most likely not be like that, even with the same curvature.
Looking wrong in this context is the discrepancy between what your brain is used to and the visual input it just receives.
And since this is a still life for a client I can't deliver the images like that and need to find an easy way to fix this.
The Nuke gradient which came up here earlier usually receives some blur and the "white line" is gone. On the geometry it's much more tricky to blur for instance the shading. Probably some kind of highpass or deltamush approach on the normal might help. I'm just checking the sample files you provided.