Occlussion Culling not working as expected

Here is a simple blender file.
https://file.io/8pTn0rkK2GXK

My best result is something like this:

I am expecting the cube to be fully deleted.
I am expecting the sphere only keeps the upper half, nothing else.

I get the same result with step files, where certain faces that are clearly not visible are not being deleted.

Am I missing something?