As stated in the title Earthern heritage transmogs are able to be used by all dwarven races in the game.
This should be reflected by all races, such as Tauren and Highmountain Tauren / . Orcs and Draenor Orcs and so on, they should also be able to share heritage armor
You can’t have it work for 1 set of races and not the others. Either have it for all, or not at all.