I am sorry but this will not work the way you think it does. It needs to merge with living tissue on the exit sire of the wound.
This is an interesting area of exploration. On a thread graft, is it a requirement to remove (or NOT remove) the cambium and phloem of the “scion”? If it is intact, how does the inner cambium, phloem, and xylem fuse for transport? If it is removed, then is it the inner cambium and phloem callousing at the exit site that create the connection to the phloem and xylem? Is thread grafting even done in commercial horticulture?
In a non-thread graft, the cut site supplies access to cambium, phloem, and xylem of graft scion. I assumed they all made connections to the corresponding tissue on the host plant. But apparently the callus formation at the union site can be responsible for eventual tissue differentiation into phloem and xylem which creates the vascular connections. But the callusing isn’t an absolute requirement in some plant species.
It isn’t clear to me how the phloem and xylem connection and transport occurs. Here is a great paper exploring the process.
Melnyk, CW. Plant grafting: insights into tissue regeneration.
Regeneration. 2017; 4: 3– 14.
https://doi.org/10.1002/reg2.71
“Callus and tissues surrounding the cut differentiate to phloem and xylem before the vascular strands are connected between scion and stock”
“Together, these data suggest that callus formation at the graft is not an absolute requirement for successful graft formation or vascular connection. Callus formation is important to promote grafting for many plants (Garner & Bradley,
2013), indicating that the importance of callus may be species specific. Whether callus is a cause or consequence of successful grafting remains unknown.”