It failed...
Actually, it worked: the grafted branch was severed from the pot, and after ten days or so, it was continuing to develop. So I removed the buddy-tape, and moved the pot to my working bench. Unfortunately, if the branch was not fully sealed to the trunk and since it was quite long, its weight caused it to fall from the trunk.
Precipitation=trouble, I should have known.
But this year, I spotted two small branches starting to grow lower down the trunk, so I decided to defoliate it except these two branches.
July 3rd:
Only ten days later, it already had a lot of new leaves.
July 13th:
But what struck me was this first branch on the smaller tree: much too straight and big. There's at least a twig that might replace it. This is a virtual I made:
What do you think: shall I remove it or not?...
Another picture taken this morning: