Joe,
indeed, and in fact I only took that on board shortly before your post! I just checked the Bekleidungsvorschrift für Offiziere... of 1911 and that quite explicitly regulates that Prussian General officers and General Staff officers seconded to Württemberg wear Württemberg uniform and conversely Württemberg General officers and General Staff officers seconded to Prussia wear Prussian Uniform. Medal bars, however, seem to be a different proposition as (in this case) General v. Wundt wears his awards in the Württemberg order of precedence.
Regards
Glenn