[lugerholsterrepair]

Doug, My question is how did they wear the holster only on a belt if the loops on the back were parrallel to the waist belt.

The "loops on the back" I believe you are referring to is the stock strap attaching block. On an Artillery holster it does indeed run parrellel to a waist belt.
The German solution to retaining this block for future attachment to a stock and wearing the holster on a belt was to slip a couple of 3 inch straps into either side of the block, attaching them at their ends to themselves with a stock strap stud. This simple apparatus enables a belt to be threaded thru them and carried in the regular fashion. This does not allow for the stock to be used though.
George explained above that the stock and holster could be carried by threading the belt thru the stock & holster, using the top stock strap as a keeper.

Jery Burney