These differences are because of the rolling transition from 5th to 6th generation and because the Jetta station wagon is very popular in Europe but is called the Golf variant there.  VW is updating only the look of the wagon (without updating the underlying body) to keep all models called Golf looking the same.  The model name "Jetta sportwagen" will be also replaced with "Golf Wagon" in Canada.  Therefore, the station wagon will be called Golf wagon/variant everywhere except the US, where it will be called the Jetta sportwagen.

The 6th generation PQ35 platform is a refinement of the 5th generation platform.  Manufacturing efficiency through economies of scale is why the Jetta sedan also gets some minor interior updates.  The Jetta will transition to an all new 6th gen body and a new platform in 2011 at the earliest.  This platform is supposed to underlie the future 2010 Audi A1, 2012 Passat, and future Audi A4 and TT.  Since the 6th gen Golf will continue to use an updated 5th gen PQ35 platform, this represents a split between the Jetta and Golf because they shared bodies/platforms in the past.  Since the Jetta wagon is known in Europe/Canada as the Golf wagon/variant, it's not known if future wagons will be built on the Golf or Jetta platform.