Nothing was forced on him by the Nazi regime. He could easily have volunteered for front line service. No German military personnel were ever court-martialed for refusing to kill Jews. He wanted a relatively cushy and safe post. Saying he's sorry now is meaningless.
Apparently he not only volunteered for front line service, he was wounded there . . . so much so that when he recovered, his request to return to his combat unit was denied. That all might be B.S., but it is probably documented.
I am guessing that you didn't read the article. He was wounded on the Russian front by a grenade. His company commander and the medical staff ruled him unfit for active duty. He was transferred to the camp as a guard rather than being discharged.