My speculation is that this is because the MP44 was made of more complex multistage stampings, its production was more automated, while the VG 1-5 was designed with a view to cottage manufacture (rather like what Chuck is doing here, with all of us gawping over his shoulder as he works). Anyone may check my translations, too.

Part 1 The Genesis of the Volkssturm Carbines. Why? http://weaponsman.com/?p=14262

Part 2 Volkssturm Carbines, part 2 of 2 http://weaponsman.com/?p=14665

The other interesting take-away was that it was again, according to the documents, Hitler who suggested the short magazine, specifically so that riflemen would be less exposed in the prone firing position. I has always assumed (that word!) that the occasional short mags were meant for lab and workbench use, even though that didn’t make much sense, because they’re more often found with rare or prototype firearms.