I don't think the referee is obligated to explain every single call to the coaches and players. The ref's job is to make the game flow. Blow the whistle, signal direction, encourage quick restarts.
I've had coaches say "Hey ref, what was the call?", after totally obvious trips, in plain view of all 22 players and all the fans.
Of course half the fans thought the player in possession merely tripped over a sprinkler head.
