Yep, all the shaders have some form or level of ambient somewhere....
I set sun_color.red,green, and blue to 0 and things are still lit(that use a normal mapping shader.
I then adjusted the VIEW*.ambient, in this case the standard "camera.ambient" I set it from 0 through -100 and no change.
the shaders all reacted to point lights though...I will look at shade-c, it is the only one I did not look into...