The engine doesn't allow cross-level references as it assumes a referenced object is immediately available which we guarantee by placing any reference clusters into the same cells. This means the behavior for either non-spatially loaded actors referencing spatially loaded actors or spatially loaded actors referencing non-spatially loaded actors will result in both actors being placed into the same cell. The severity of the spatially loaded actor referencing non-spatially loaded actor message was recently downgraded to a warning as we plan to support this.