If a mixed group of War Mode and non-War Mode players tried to get together for a Mythic, they’d often find themselves unable to summon. This change should help out players that were previously having difficulty getting groups together for dungeons. You’ll still need to be in either capital city to enable War Mode, however - this change only applies to disabling War Mode while you’re out in the fields of battle.
With the update, players will be able to turn off War Mode in any rested area, instead of having to travel to Stormwind or Orgrimmar to do so. It looks like War Mode may be getting a little change in WoW’s patch 8.1, according to a recent update on the PTR.