I noticed this issue when I was messing around with my lighting settings and decided to turn it to all dark as I noticed in more typical lighting conditions it was darkening the material below it.
Just realised that even w/o the NormalMap the middle does not change depending on material selected
Only the colour selected can be seen, if anyone knows why this is please help.
EDIT: Using the devforum post below I am able to get the middle to be transparent when not using SurfaceAppearance, but I really want to be able to use a NormalMap which requires SurfaceAppearance to be used.