Until a phenomenon is understood (studied and published in scientific journals) a “proper” name for the observation may be quite muddied in the literature, both scientific and hobby publications.
I suspect that folks are looking at the issue(s) grafting and sharing or transfer /translocation of symbiotic primary producers and clarification of terms will follow debates and conclusions that are not yet published?
I suspect that there is a simple process where two corals living in the same tank can exchange symbionts by physical contact and there may be a separate process where coral collect and incorporate symbionts that were caught in the current born drift?)
The pictures shown in the article appeared to indicate the latter situation?
I agree that the commonly used term from gardening; “Grafting” is possibly misapplied in coral discussion but what it should be called is not necessarily obvious until the process is understood and described, at which time the scientific writer may provide us with a proper term(s) for what people now commonly refer to as “Grafting” in the hobby.
I might propose “symbiotic Drifting” but I will wait for the literature to catch-up with my observations and accept or reject the term as is proper?
Hth