They chose it because it’s one of the most gushed-over expansions next to Wrath and Legion, and they had a bunch of unused recolors of MoP gear, mounts, and pets that were sitting in the files and could easily be repurposed as goodies to keep casuals subbed until TWW.
Remix is time-sensitive filler content, not something that has any bearing on the plot of the next three expansions. It’s about observing the past, not bringing things back from the past into the present, and is not going to have any allied races linked to it, just like it wasn’t all the other times this idea was brought up: