Is this a bug? Standard assets water reflection occlusion culling matrix.

I was having issues with object disappearing in the reflection using the standard assets WaterProDaytime prefab. If the main camera wasn't looking at the object it was being culled from the reflection camera.

After digging through Water.cs I found this on line 103:

 reflectionCamera.cullingMatrix = cam.projectionMatrix * cam.worldToCameraMatrix;

changed it to:

 reflectionCamera.cullingMatrix = cam.projectionMatrix * cam.worldToCameraMatrix * reflection;

and the problem went away.

I may be missing something, but I figured that cullingMatrix should be reflected the same as worldToCameraMatrix. Is that a bug or is there something else I should have fixed elsewhere in my scene?