What is the point of the Layer in Post Process layer component, its useless

I'm not understanding how post process volume script and the layer section on post process layer script component works. It seems impossible to apply anti-aliasing and post process effects to certain layers. If I create a new layer, say layer 13 and set global volume to the same layer and set the layer on post process layer script to use layer 13, every layer gets post processed. How do I exclude game objects from post processing that are on different layers. What is the point in the layers section if it Globaly applies to all layers no matter what layer is selected.

 

The layer is not for objects in the scene that you render. As I understand it, it's only for your post processing volumes. Evidently having all of these on a separate layer is just an optimization for blending the post processing volumes faster? Someone correct me if I'm wrong.