Time travel up until Warlords of Draenor has always been that potential timelines were not the "True" timeline. Why is this one being treated differently? It's dumb.
In the Mag'har recruitment quests, Oculeth sends us to Alt-Draenor. But. If the warriors they allied with from other timelines were just as real and persistent and non-echoey as the Mag'Har, why wouldn't they just go to Azeroth five minutes into the past, and recruit the entire Horde all over again? Just gather a consistent stream of fighters who we are already allied with, rather than worry about the effort involved in recruiting one new race.