Hi YHWH,
When MoI creates the polygon data, it creates the vertex normals from the original NURBS surface.. Once it has been transformed into a poligonal object, the calculation then has to come from a faceted, non-curved surface (groups of flat polygons) and can lead to shading glitches.

A NURBS object is a mathematical representation of true curvature. A polygonal model is a group of flat surfaces that represent curvature (small or large facets determine the approxamation).