It is impossible to know the particulars of this specific incident and it may be that mistakes were made by both the diver and the dive op. We can just be glad that there were no fatalities.
But it makes me grateful for the excellent and thorough boat orientation that is given to all new arrivals by the Reef Divers op in the Caymans the first time you start a new trip with them. It doesn't matter if you have dived with them in the past, they review all of the boat/dive operations and especially the safety procedures when you start to dive with them - either as a repeat or for the first time.
Each of their boats is equipped with a very loud siren and voice system that can easily be heard underwater. They turn it on so you can listen to it for short time during the boat orientation. They use sound signals and emphasize that if you hear the diver distress siren you must "stay down, don't surface!" because they are going to move the boat, and they tell you what to do in various scenarios - whether it is you or someone else who requires assistance.
I wish that this was the standard equipment and procedure for all dive boats.