^^I suspect this is the answer.^^ Or at least that he hasn't been in a game that has had dissent sanctioned before.
Obviously the coach should know anyway, but certainly in my experience (as a parent of two youth players), sanctions of any kind seem to be extremely rare in youth football, and the coach could easily have coached for several years without seeing any sanction at all, never mind a temporary dismissal.
I reckon I have seen my children play in at least 150 games at aged U12 or above since temporary dismissals have been in existence, and have seen a fair amount of sanctionable dissent, but have only seen a single temporary dismissal issued [just a few weeks ago in an U16 game (following repeated aggressive dissent throughout the game by the same player)].
It isn't just temporary dismissals though, it is all sanctions.
In the same 150+ games I think I have additionally seen 2 dismissals and at most 10 cautions for all reasons [playing and non-playing] (almost all of which were during matches at aged U15 or U16).
In watching over 500 games at U11 or younger I don't recall seeing a single caution or dismissal despite plenty of sanctionable behaviour.
For a larger sample: The junior club for which I volunteer (currently with 18 teams from U7 to U16) has received just 4 dismissals and 24 cautions in total in the past 9 years [figures from Whole Game System, so if any were not officially reported they will not be included]).
They are a well-run club with the right attitude and do weed out the problem players & coaches fairly effectively, but I don't think they are particularly unusual / an extreme outlier.
Just to be clear, the above is just to give some context and is not in any way intended to suggest that the OP shouldn't have sanctioned. Quite the contrary, I can't abide dissent and (coming from a rugby background) would like it more effectively dealt with at all levels of the game.
we've been on an upward trend from there
