OSX 10.13.3 /// GTX 980Ti x2
Worked: Some other users report to have it working properly using the same version.
Short description of error
Using a special node setup in order to visualize some custom matcaps show a different result in comparison to some other users. It appears flat while it works perfectly fine for other users with the exact same project and Blender version. It looks perfect when rendering.
Exact steps for others to reproduce the error
Open the attached project and it should look like a matcap is being used in material shading. Next picture shows my result on the left and the intended result on the right which I can only achieve in render shading.