HH was supposed to have been a comedy (albeit a strange topic for one), not a realistic depiction of life in a Nazi POW camp, so considerations of historical accuracy and continuity were not particularly important. At the time, the fact that it became so popular given its theme was very surprising. I suppose life in a German POW camp as depicted in "Stalag 17" or "the Great Escape" was more accurate. Long ago in the mid-1960s I worked with an ex-GI who had been interned in a WWII German POW camp. He was still bitter over it and hated anything or anyone German. I don't know, but I suspect he was not a fan of HH. Nonetheless, life as a POW in a German camp was pure luxury as compared to conditions in a Japanese POW camp. Very few American POWs ever got out of those alive. On the other hand, German POWs held in American POW camps in the US had a relatively soft life, and many of them even wanted to stay in the US after the war.