Is there a reason all of the Broken Isles PVP zones belonging to the Horde are comprised of Forsaken?

I'm not a PVPer so maybe it is linked to PVP modes, but I've been doing the world quests in the PVP towers to work towards my artifact appearance. As an Alliance player fighting Horde towers, I noticed ALL of the NPC enemies are Forsaken. What's that about? Only reason I can think is Sylvanas is Warchief but that doesn't really make sense either, unless she is planning a hostile takeover of the Horde so she's arming the undead. Unlikely though.