This image is interesting, and theoretically it helps. But in practice I don't understand how the same size cut could have either the result in the second or the third drawings - seems to me it should be one or the other. That is to say, the cuts in the second two drawings appear to be almost the same width, but one has the cambium only on the edges, the other has it in the middle. I don't see how the same width cut could have two such different results.
The cut that Mr. Zill does for the second graft in the video looks to me like it should turn out like the second drawing, requiring lining up at least one side. But he centers the scion a la the third drawing. That's what has me confused.
I'm no expert on grafting either but I'm doing my best to learn. The two drawings to the right in my previous post illustrate cuts at slightly different depths with the second one cutting along the cambium. In both cases however, the rootstock bark layer is thicker than the scion bark layer - because the scion is a smaller limb and additionally the rootstock layers are cut at an angle which makes them appear even thicker in the plane of the cut.
Zill describes the cut between 5:15 and 6:15. His first cut appears to go through the bark and into a lighter color layer but he says it isn't deep enough and cuts more off, then points down the middle of the removed piece and the cut on the rootstock to a slightly darker area that he calls the cambium and describes as "juicy". I suspect that the confusion may come from assuming that the "bark" is just the dark layer on the outside whereas this isn't really the case. Cambium layer cells produce layers of phloem cells on the outside of the cambium that are alive and growing. They are the cells that form the transport system for materials up and down the stems and trunk and are usually whitish. This is the lighter brown ring in my diagrams.
This page illustrates the 4 possible layers of bark outside of the cambium - phellem, cork cambium, phelloderm and phloem. The phellem is the only dark layer.
This video has a good general explanation of plant growth, including the secondary growth accomplished by the cambium layer.
This page has a photograph of the section of a trunk identifying the cambium and inner bark (phloem) layer. If you magnify the image you can see the outer bark is a darker color.