@Romullus, I submitted the texture set to the private uploader if you'd like to take a look for yourself. The question the post is asking is whether it is more "correct" for the normal map to be plugged into the Base Material, Layer 1, or both the Base Material and Layer 1 for a Corona Layered Material. As you can see, the surface response of the material is different under all three of those conditions, but which is the correct method?
The texture set represents both a dielectric and metal surface, i.e. there are not separate textures representing the metal and wood surfaces, the surface is represented by a a single texture set - that is why the texture set is parsed into a Corona Layered Material with two sub-materials: a dielectric and a metal.
Importantly, in the above comparison post, the normal map IS plugged in to either the Base Material or Layer 1, i.e. the post is illustrating the visual difference. Disabling normals from either the Base Material Layer 1 is not depicted.