I agree, but this one was more obvious than most. It wasn't intentional obviously, but the end result was a forearm smash straight to the jaw. Once it was reviewed they're always gonna call that.
It's just a flow on effect from the TMO protocol, sometimes they're gonna spot things that'd be let go in real time - e.g. Naholo's also high tackle. A similar example was in the Canes v Brumbies game - Barrett indulges in some fairly soft rucking to a Brum lying on the ball. Would have been let go but for the fact that it was close to the line and the ref checked if Goodes had scored a try.
As for the 'naughty seat' it was a bit unfortunate, but the Laws seem to indicate refs have to be a bit harsher when it's a PT situation.