Light source angle does not work with regular stationary shadows. These work similar to the dominant directional light shadows in UE3 which also did not support adjusting the light source angle.
It does however work with static shadows as well as the new sphere-traced distance field shadows, which is why the setting is also available in UE4.
“Only self-shadowing” is not a available in UE4 as it is very inefficient to achieve in a deferred renderer.