I've said this in other forums and been smashed for it - but it's the only logical sequence of events. Kosi knocks-on through no fault of the defensive pressure and gets smashed in the chest by Katoa. Sure, it was a heavy hit and could look high, but it's something the bunker would need to sit and investigate for 5+ mins (not going to do that during a live game), so leave it with the MRC. Award the try, and let the MRC deal with the fine details of if Katoa should or shouldn't miss games.
It now sets the precedent for the following scenario:
Panthers vs Melbourne in the GF. Scores locked up at 20-all, 79th minute. Big NAS comes charging at the line 5m out running onto a Harry Grant pass, NAS boggles the ball and knocks on, as he's going to regather, JFH belts him similar to Katoa - right in the chest with his shoulder and levels him. Burton scoops up the loose ball and races 95m to score under the sticks. Crowd erupts, Panthers win the GF. Bunker steps in, same fool that was covering our game, and rules a penalty for a 'high shot' that wasn't in fact high. Melbourne takes the 2 in front of the sticks and wins the GF.