This behavior is intentional. The CullingGroup.IsVisible() method determines the visibility of a BoundingSphere based on the data from the PREVIOUS frame. Since your BoundingSphere array is static and shared across various Culling game object instances, the visibility result you're observing is not immediately updated. When you update a BoundingSphere's position, its culling result for the current frame isn't yet computed because the camera hasn't commenced culling for this frame. Therefore, you receive the visibility status from the last frame, where the BoundingSphere might have been in a different position and consequently culled.

To address this, consider checking visibility in the OnRenderObject() method instead of LateUpdate(). By the time OnRenderObject() is called, culling is complete, and you have the accurate visibility result for the current frame.

If you prefer to continue using LateUpdate() for the visibility test, ensure you delay the first IsVisible() call and destruction of a newly created object by one frame to avoid immediate deletion. The corrected implementation in OnRenderObject() would look like this:

void OnRenderObject()
{
if (!IsVisible())
Pool.Destroy(gameObject);
}