Try or no try is the most general thing a referee can ask for. It covers everything.
If they only want them to check the grounding they can ask for that or if they only want a knock-on checked then they can ask for that.
Yes but the TMO answered with probable try. By doing that he can skip the knock and just look at the foul play. Wrong answer to the question which skips the knock on. The knock on would make the holding back irrelevant.
Every question have a jurisdiction of the protocol.
1) Is it a try – yes or no?
1. Potential infringement by the team touching the ball down in opposition in-goal
1.1.
If after a team in possession of the ball has touched the ball down in their opponents in goal area and any of the match officials have a view that there was a potential infringement, of any nature, before the ball was carried into in-goal by the team that touched the ball down, they may suggest that the referee refers the matter to the TMO for review.
1.2. If the referee agrees to refer the matter to the TMO he will indicate what the potential offence was and where it took place. Potential infringements which must be CLEAR and OBVIOUS are as follows:
Knock-on
Forward pass
Player in touch
Off-side
Obstruction
Tackling a player without the ball
Foul play
Double movement in act of scoring
Referee judgement calls for all other decisions in the game are not included in the protocol and may not be referred to the TMO.
In reviewing the potential offence the TMO must use the criterion on each occasion that the infringement must be clear and obvious if he is to advise the referee not to award a try. If there is any doubt as to whether an offence has occurred or not the TMO must advise that an offence has not occurred.
For forward passes the TMO must not adjudicate on the flight of the ball but on the action of the player who passed the ball, i.e. were the player’s hands passing the ball back to that player’s own goal line.
2) Can you give me a reason why I cannot award a try?
2. Potential infringement by the defending team preventing a try from being scored.
2.1. If the match officials have a view that there was a potential infringement by the
defending team that may have prevented a try being scored they may suggest that
the referee refers the matter to the TMO for review.
2.2. If the referee agrees to refer the matter to the TMO he will indicate what the
potential offence was and where it took place. The offences will normally be an act of
foul play such as obstruction or playing a player without the ball.
2.3. In reviewing the potential offence the TMO must use the criterion on each
occasion that the infringement must be clear and obvious and that but for the
infringement a try would probably have been scored if he is to advise the referee to
award a penalty try. If there is any doubt that a try would be scored the TMO must
advise the award of an appropriate sanction in accordance with Law.
2.4. The TMO may mention issues viewed in addition to those requested by the
referee if it is appropriate to the situation under review.
3) But for the act of foul play – probable try or no try?
3. Potential acts of foul play
3.1. The match officials may suggest that the referee refers the matter to the TMO
for review if they observe an act of foul play where:
They may have only partially observed an act or acts of foul play
They are unsure of the exact circumstances
The views of the match officials reporting the act(s) of foul play differ
There is doubt as to the appropriate sanctions to be applied
3.2. If the referee agrees to refer the matter to the TMO he will indicate that he
wishes the TMO to review the potential act(s) of foul play and to make a
recommendation as to the appropriate sanction(s).
3.3. In reviewing the potential offence the TMO must use the criterion on each
occasion that the infringement must be clear and obvious especially where sanctions
may apply where a player is removed from the field of play either temporarily or
permanently.
3.4. The other match officials may utilise the in stadium screens (where available) to
form a judgement in this matter.