Occam's Razor: why would anyone who wants to exterminate a race even bother with death camps at all, especially a people known for brutal efficiency? So they could torture them first like cartoon villains? Yeah, okay.

At least the Japanese Unit 731 were performing horrific medical experiments and weapons testing on live subjects to gain scientific knowledge, not just to twirl their mustaches like history books and 100s of pedowood films would have you believe.