Well, that's what they always say. No other witnesses for obvious reasons, so there is just his statement that "he didn't see anything".
That's what they always said and what they will always say until the last one of these SS - for which one had to sign up voluntarily btw, at least in the early 1940s - war criminals dies.
And btw, the court clearly stated that he signed up
voluntarily.
German source here, run it through Google Translate or so:
https://www.nwzonline.de/politik/niedersachsen/meppen-oak-ridge-nazi-verbrechen-karteifund-usa-weisen-ss-mann-aus_a_50,7,2254340105.html