Maybe he did, but the deniability was indeed plausible. And I'm aware that many doubt his sincerity, and it's perfectly reasonable to do so. That being said, I find his explanation not just plausible as well but more useful as an explanation. People chose not to see or believe what was too inconvenient. See cognitive dissonance. That explains how the Nazis got them to do what they did. Note that I'm not saying that they were ignorant of every crime, just that they were spared the undeniable knowledge of the most offensive ones, making it easier to support or at least fail to oppose the régime. Deporting the Jews was bad enough, and that was done in plain sight, but not quite as unpalatable as their mass murder.

The point here is that Japanese soldiers were massively trained to perform horrible things. They mistreated prisoners of war, civilians, anyone, everywhere, and new recruits were forced to perform horrors as part of their induction. Germans on the other hand respected the rules of war in the West (though certainly not in the East) for instance, except obviously for the SS. They were certainly keen to appear legit in that respect. The Japanese were not, ever.