^ Yep. The most common way it is done is by accident. Some reefers manage to actually find two of the actual same species and manually do a graft, but that comes down to even more luck IMO.
there was a member in my local club that was using insulin needles to take Zooxanthellae from one coral and inject it into another. im not sure what happened from it but very interesting
there is talk that most of the "rainbow" chalices are made from a type of grafting bassicaly they throw a bunch of chalices into a cove and they naturally share Zooxanthellae