Teams change, teams are inconsistent. I don't agree; if a referee coach has something valuable to say that will improve performance then say it. Referee doesn't have to listen, the same way that the players sometimes don't.
Coaching has its place. However, care is needed. As I posted earlier, the idea of this tournament is development. For the players and for the referees. It therefore makes some sense to include an element of coaching.
So if this was the actual match appointments with, I'm assuming, a late change of referee, why would the TMO feel the need to "coach" the referee if there was a designated Assessor? That seems like a relevant question for some here but one I'm not comfortable with. I've never heard of a TMO acting as a referee coach. It simply isn't their job. I'd also be surprised if the appointed assessor had anything "coaching" to say at half time even if there is a "development" element to the competition.
Just trying to imagine what kind of reception he would get from Angus Gardiner if George Ayoub was making comments like, "Try standing at the front on the next green lineout Gus. I think it would be a better position for you", or "You may need to scan the blue backline more at the rucks Gus".
Leicester Tigers vs Northampton
Referee: Ben Whitehouse (Wales)
Assistant referees: Jonathan Healy (England), Ross Campbell (England)
Assessor: Gary Welsh (England)
Television match official: Neil Hennessey (Wales)
Timekeeper: Paul Stanley (England)
I suppose my post-match debrief is a sort of coaching, but I never offer comments during the game. Occasionally a ref will ask at halftime how things are going, but I simply say that I only suggest changes if there is anything dangerous. So far I have never had to do that.
The TMO's position is not that of a coach, whose job is to improve the referee's performance for the future. He is merely there to help with a specific incident. I agree it is awkward if his view of the correct decision is not shared by the referee, but ultimately 6.A.4 (a) prevails.
BTW the referee at top level is assessed in detail after each game - does anyone assess the TMOs?
In England the TMO is very much part of the referee assessment process with all participants commenting on both his contributions and omissions. There is also an external assessor (outside the RFU) who gives independent feedback. Bad performance by the TMO can lead to removal from future fixtures as it does with referees and ARs. TMOs also meet every 8 weeks for a peer review.