Those are some big colonies they are harvesting, interesting to see and thanks for the link. While one company that operates in this manner might be sustainable I wonder what the impact to the reef would be if several companies were harvesting this volume from the GBR.
Swapping frags with hobbyist is so great for this reason, no new harvesting needed but of course there is the impact from the initial wild harvest that got the coral into aquarium trade in the first place.