For me it looks like he cuts a line right down the middle of that “nub” cut.
On the scion after he has completed the angle and long cut, he exposes the cambium on the sides of the scion where there currently still is bark. You do that by allowing the knife to do the work and it will shave off the bark in such a thin strip that it’s less than “paper thin.”
Then the scion is inserted.
What you would furthermore look at carefully is how much more contact could potentially be made by shaving off more bark as you round the scion over (slicing more thin bark layers) on the side with the bark. So when you fold it all together you achieve maximum contact with the “winged” flaps of the rootstock.
It’s definitely a different method of bark grafting. Because… you’ve unfolded the insert area like opening up a book. That’s my reference to “wings.” Then when you close the book, you want the scion to have as much contact as possible “with the pages on each side…”
Oh yes, also on the back side you do make a 1/4" or whatever cut at the tip. And that is inserted under the bark.
It should be assumed the long cut on the scion is completed and turned over and a 1/4" or 1/2" “wedge cut” is completed. Then the book can be opened and the skimming off of the bark can be done; and finally it is all folded together. I think that’s called the enchilada grafting technique.