Occulusion Culling Area explanation in manual is confusing

Hello,
I'm a bit confused as to the what checking the "Is View Volume" checkbox on the occlusion area component.
The manual says: http://docs.unity3d.com/Manual/OcclusionCulling.html
After creating the Occlusion Area, check the Is View Volume checkbox to occlude moving objects.

It then goes on to say:
Is View Volume: Defines where the camera can be.

Then it says:
To apply occlusion culling to moving objects you have to create an Occlusion Area
NOTE: By default if you don’t create any occlusion areas, occlusion culling will be applied to the whole scene.

1. So the manual has conflicting explanations of the purpose of "Is View Volume"
2. According to the wording, if did not select "Is view volume", then the occlusion area should do nothing, and is useless.
3. First it says you need an occlusion area for dynamic objects, then it says you don't need an occlusion area for dynamic objects.
4. After testing, dynamic objects are still occluded by static occluders, even without an occlusion area. There doesn't seem to be anyway to prevent this from happening.

I can't wrap my head around this.
Could someone explain on why an Occlusion area would be used, and what the "Is view volume" does?
Thank you.

 

I'm confused too. Hope someone can make it clearer