Baking lighting with “Use normal map for static lighting” option turned on and off produces almost identical results - normal map doesn’t contribute to baked lighting and yields improper shading (as if it was a low poly mesh lightmapped, no details normal map should provide are visible).
This option in the editor is not for just any normal maps in the game. It’s for specifically built types where lightmass would need to know how to address.
As a test case, if you have a cube with all faces using a single smoothing group, but then render out a normal map to achieve sharp faces. Lightmass will need to be told about the normal map to reconstruct that as a cube with sharp faces. This is where this option comes into play.
Is this resolved? I use Version: 4.13.1-3142249+++UE4+Release-4.13 and have problems with baked lighting on static meshes with one smooth group and baked normal map. When I change them to movable the shading is perfect.