So he concaves the top of the chop, allowing the branch to be bent over the center of the chop instead of off to the side???
Totally want to see a top view of this immediately after its executed.
No bending anything. And ~concave, yes, but just slightly from flat or if edges are too thin they dry out and die back and take longer for the bark to grow over the open wood,
if at all. The emphasis is on tapered to a point that contributes to overall taper of the trunk to a pointy tip-top. All this depends upon having a live twig to wire vertically,
very near this pointed end-of-chop, without which most or all of this chop will die back and be a useless exercise.
Now comes a debate about applying a sealant on the fresh cut wood, or not. I always apply paste to open wood area of greater than 1 square inch so it doesn't dry out before growth can occur. The thinner the section of wood below the living bark, the quicker it dries out. Also, I believe it is better to do this when the sap is presently flowing to growing leaves than in autumn or winter when the wood is naturally drier. There will always be a temptation to do a higher degree of taper than is wise. The base of the twig needs to be undamaged by the bending upward and wiring, too. The top of the tapered cut near the base of the twig needs to be substantially wider than the base of the twig for the twig to be undamaged when you bend it upwards. 45° cut is much safer than a 60° cut, and anything that is greater and looks really pretty is probably a death warrant to that exercise and you'll wind up with a stub at the top that needs to be overcome by many years growing.