And I just wanted to add that a plant beginning to grow does not necessarily mean that the stalk and the root merged.
All it means is that the extra root kept the plant hydrated long enough for the cutting to grow its own roots.
It'd be really nice to see what was going on inside the soil, instead of speculation about it.
I did this with about 7-8 cuts last week, and not a single one has shown any growth in the original root mass. The cuts themselves are growing tho
i only grow mine in water and i use a microscope all the time.. the main grafted root does indeed grow again after the shock.
and grafting is indeed key.. a wrong graft can ruin the whole plant. but if you take ur time you should be fine..
btw this method is great for really hard to root clones.