Hi FlashFire, yes there are definitely problems with vertex normals and Blender - Blender just simply ignores vertex normals stored in files and also discards them at other times as well like when doing renderings.
Because of this, Blender is just not very good at rendering CAD data in general.
> Maybe to get a model ready for resale for use in popular 3D
> software, it requires retopology afterall.
Well, this problem is pretty much limited just to Blender - all other renderers that I know of are able to read in vertex normals and use them for shading.
For Cinema4D use OBJ format, C4D is able to read in the vertex normals stored in the OBJ file, it will be present as a "normals" tag in the model data.
