As was pointed out already - the call was from several minutes earlier before we even had the call and it was a contentious call at best given it was a decoy runner.
By the logic of that time frame you might as well have the refs go over the game after it's finished and adjust the score after forensically checking to ensure every single decision is precisely correct.
No, the TMO protocols don't work like that
For Foul Play, the Referee, ARs and TMO can go back as far as the last time the ball was dead (e.g. in touch or the game was stopped for some other reason), but no further.
For other types of non foul play infringements such as a knock-ons, forward passes, offside, hands in the ruck, not rolling away, side entry, not releasing etc, they can only go back two phases (being the current phase at the time the call is made, back to the second most recent ruck, maul. In the examples below, they can only go back as far as the red
ruck
ruck : open play (knock on) : ruck : open play (try scored)
- Try disallowed for the knock on
However..
ruck : open play (knock on) : ruck : open play : ruck : open play (try scored)
- Try stands
Also, of course, you cannot adjust the score without affecting the play. If you retrospectively disallow a try, this would have resulted in the game restarting in a different place (penaty, 22 droput, lineout instead of a halfway restart). This means you cannot predict how that change will affect the rest of the game.