Saurfang was never a coward until BFA of course. He was never mopey like he was in BFA. Saurfang was never a traitor like he was in BFA. He had his own beliefs but, like Nazgrim, respected the Horde and its leaders. He was still part of the Horde in MoP and worked WITH THE HORDE to deescalate the Garrosh situation. He didn't run to the Alliance or sat and cried when things did not go his way.
In BFA, he works with the Horde and actively plays a major role in igniting the war. He agrees with Sylvanas that the Alliance will attack sooner or later and Saurgang is the primary reason for Horde making it to Teldrassil. He turns a blind eye to the massacre committed by Jaina and the Alliance on Dazar'Alor. He turns a blind eye to the assassination of King Rastakhan. He turns a blind eye to Baine murdering Horde guards to free Derek. The worst part is he aligns himself with the Alliance after all this instead of trying to unite the Horde.
Basically, he starts the war. Makes Sylvanas the scapegoat when shit hits the fan. Cries and aligns himself with the Alliance.