I just finished Blood Red Snow on a recommendation of this sub. Really interesting read, and a perspective we don't see much. Nevertheless, I was struck but what an immense stand-up guy Koschorrek was at the time. Aside from killing Russian soldiers, he never witnessed/participated in any atrocities on civilians, instead only seeing the aftermath of what Russians did to their own people. He even lets some captured Italian partisans go instead of shooting them as ordered. Generally, he makes little to no reference of anything wrong the Germans may have done, which really irked me. Similarly, Russian POWs are treated fairly in his version, even receiving medical attention, while German POWs are shot.
The question: is it possible that a soldier serving on the Eastern Front could have had such an experience? Or is the consensus that Koschorrek engages in selective memory to appear more sympathetic?
The account of Korroschek's views you give is certainly at odds with German policy on the Eastern Front. Regarding POWs, for instance, the most concentrated (in the sense of deaths vs time) period of mass murder during WW2 was the deliberate starvation of 2.8 million Soviet POWs in just seven months between July 1941 and January 1942.
Now, as regards Koschorrek's account - I've not read it - what would perhaps be useful is to find what unit he was in and see if you can find an operational history. When you know his movements, you can cross-reference those with reported warcrimes and see if he's being accurate.
However, contemporary research has totally exploded the 'clean Wehrmacht' legend (this post on /r/badhistory goes into some detail how) and you should know that if Koschorrek is telling the truth then his experience is extremely atypical.