Does foliage frustum culling work by culling all or nothing?

I’m doing a VR-application using HTC Vive. I have a landscape with a lot of foliage all around, added using the foliage tool. When looking at the framerate, the fps drops to half as soon as any part of the foliage comes into view. The fps are pretty much the same no matter how much foliage is in view.

It makes me think that all the foliage is rendered as soon as any foliage comes into view, even the foliage that is behind the camera.

I used the console command freezerendering to see what is rendered behind the camera, and sure enough there was foliage when I turned around.

Am I correct in thinking that foliage culling is all or nothing or have I misunderstood or am I doing something wrong?

I think we are experiencing the same thing. Where you able to find a solution?