To answer your question the difference is the ones in Shadowmoon are the Wildhammer that were part of the Alliance Expedition to Draenor 20 years ago during the Second War.
The ones back in hinterlands are the Wildhammer that stayed back home and ultimately broke away from the Alliance.
You can't see them in game but there is a third faction of Wildhammer that were part of the Alliance during the Third War, they live on Mount Hyjal currently.Baggins 13:57, 21 June 2007 (UTC)
Happy now? Edit
00:26, 10 January 2008 (UTC)
Happy now? (2) Edit
04:30, 10 January 2008 (UTC)