No ref sends it up as a try without having seen a grounding - except Ben O’Keeffe.
I don't think this is true. Plenty of maul tries get awarded on the basis of probability that there were no defenders in the way of getting the ball down although the referee also didn't conclusively see a grounding.
I agree that BOK made a shocking decision in that Blues vs Tahs game with the help of the assistant.
I also agree with Nic Berry's decision here. He didn't see a grounding and it was a defender that was trying to prevent it. He shouldn't award it without seeing the grounding.
If Berry had awarded the try it would have stayed a try. Likewise if the laws were different and it gets sent to the TMO with no decision made by the referee I think it stays no try because there is no evidence that one was scored.
I think the current process is fine. I'd prefer referees to make a call and then it gets confirmed or overturned.