translate English to French: As acting CCO he would not necessarily have heard about the work a Supervisor had done that was excellent, but he would have heard about any negatives, either from the union or from management, eg.
À titre de COC par intérim, il n'aurait pas forcément entendu parler des bons aspects excellents du travail d'un superviseur, mais il aurait entendu parler des aspects négatifs, que ce soit par le syndicat ou la direction.