In this case, I think the template is specific to the logs diameter and the varied slopes of the planes requires two different elliptical cuts. I think that there is a close tolerance in the cuts to limit error in transfer. Also this looks like a center line layout, so the origin of the layout is on the horizontal center line. Therefore the template must extend past the critical dimension mark, so the template can be assured to register on the mark.
Since I did not witness the demo, I think that any specific comments on each photo could be wildly wrong. A number of things are not clear to me in the photos. I can guess but I'll pass for now.
