Multiple active AR Sessions in RoomPlan application, who creates them?

I am running a modified RoomPllan app in my test environment I get two ARSessions active, sometimes more. It appears that the first one is created by Scene Kit because it is related go ARSCNView. Who controls that and what gets processed through it? I noticed that I get a lot of Session Interruptions from Sensor Failure when I am doing World Tracking and the first one happens almost immediately.
When I get the room capture delegates fired up I start getting images to the delegate via a second session that is collecting images. How do I tell which session is the scene kit session and which one is the RoomCapture session on thee fly when it comes through the delegate? Is there a difference in the object desciptor that I can use as a differentiator? Relying on the Address of the ARSession buffer being different is okay if you get your timing right. It wasn't clear from any of the documentation that there would be TWO or more AR Sessions delivering data through the delegates. The books on the use of ARKIT are not much help in determining the partition of responsibilities between the origins. The buffer arrivals at the functions supported by the delegates do not have a clear delineation of what function is delivered through which delegate discernible from the highly fragmented documentation provided by the Developer document library. Can someone give me some guidance here? Are there sources for CLEAR documentation of what is delivered via which delegate for the various interfaces?