When we graft similar sized branches, we need to cut into the branches. This gives 2 thin lines of cambium. We need to line up 1 side to match the cambium.
In the video, the guy removed a big chunk of bark from a big branch. Left on the big branch was a big sheet of cambium. He did not need to line up the rootstock.
The difference is sheet of cambium versus 2 thin lines of cambium.