After looking at some (vague) recounts, it appears that the German treatment of POWs was drastically different between Russians, communists, Americans, etc.
Were there certain policies put in place by the Germans that allotted for different treatment? Was it motivated by SED principles? Much of it fell under violations of the Geneva Convention, yet there seems to be a drastic inconsistency towards Russians especially... why?
I am by no means a Historian, but I am a big WWII buff. What the Germans were doing in WWII in the POW camps were not based off any prior documentation (For the most part). There were basic knowledge and guidelines established from previous wars, especially just coming out of WWI, however what they were doing had not been done on such a huge scale before. For the majority of the Germans, the knowledge of what was going on in the camps was hidden from public view.
A lot of Germans honestly believed that the POW camps were not in harsh conditions, nor did they know about the mass executions. To the common public, they were a nuisence that were being dealt with by sending them away. There was a lot of propoganda spread throughout the country(and to other countries as well) depicting POW camps as generally not a bad place. You can still view a lot of the videos and posters today Youtube and r/PropagandaPosters is a good place to start.
As for the actual Nazi's at the camps, some STILL were being lead to believe that the conditions were not as bad as they really were. A lot of Nazi's believed they were doing the right thing for their country. Those that did find out what was really going on, well their opinions differed as well. There were Nazi's that spoke up against what was going on, but they were quickly moved, lied to, or punished (even on a minor scale). There of course were a lot of Nazi's involved that had complete knowledge of what was going on and had no problem with it. As for the inconsistencies with the Russians, though the POW camps were not as extreme, they were far from being safe havens. The Nazi's and the Russians hated eachother. Conditions were still very poor then, and a lot of the Russians did not know to what extent their captured comrades conditions were. Also, not ALL POW camps were as bad as the infamous ones; a small portion of how they POW's were treated came from the general norms from the previous wars. Back then, chivalry was more of a big deal than it is today in society. War before this was considered by many, a gentlemans game, in which they had an unspoken gentlemans agreement. It was not rare for soldiers on either side to be treated fairly, joking around, or even to drink together. "Hey, you beat me, good job!" kind of thing.
Just my 2 cents, hope this helped.