I believe it's more mundane. I doubt they actually put in writing the killing of civilians. They don't have to. All they need to do is send very poor sociopaths into occupied territories. The officers stay in basements while the conscripts torture, kill, rape and pillage in the night. Keep in mind, the concripts often aren't White Russians. They have nothing in common with Russians or Ukrainians--no love lost for either.

Thinks about it, just 10 sickos killing a few people a day and you end up with over 300 people strewn about dead after a month.

Also, there is the definitions of combatant. If you're hunting Nazis then how can you tell them from civilians? In that way, you get get soldiers to shoot at "nazis" driving around in cars.