Yes, the KGC did graft trees. I have found many examples. If you look at this picture, this is a hootowl tree with 2 vertical branches. It is an oak tree with 2 beech limbs grafted on it. Not only do you see the rough oak bark and smooth beech bark, but you also see a distinct line where the 2 contrasting woods were joined. Carvings led me to this tree. It is in the woods 2 miles deep from the nearest road. That is a very interesting area.
Good luck,
Boattow