Yes it can be done, it has been done, it will work but not always done exactly as shown in the picture used. People have taken plants and at harvest cut them more as if they were going to be revegged, leaving more than just a short stump or something, and they would graft cuttings of different varieties with very similar flowering time periods onto what low branching that was left and along with the new grafts receive a vegetative light cycle.
Basically as the grafts heal/become part of the remains of the harvested plant the remains of the harvested plant revert back to a vegetative growth cycle, not as in the same number of days, just as in both processes will be going on at once, and then at that point it is basically just a revegged plant with some different strain or strains grafted to it and growing on it.
If you are good enough and if you are inventive enough and if you really do your homework and if you like to play there are all sorts of things that can be done that are fun. The big question has always been, in the end is it really worth having done it or not?
