It’s not slavery. They’re similar atrocities though. It would be weird to refer to the people in Auchwitz-II as slaves.
While you could logically argue that people there were also slaves, it would be an injustice to leave it at that. Generally speaking, slaves had some kinds of rights that were far better than those in Auschwitz-II.
It's one thing to be treated as someone's property and forced labour, as a slave.
It's another thing to be subject to awful medical experimentation (often to death), torture of kinds that are barely imaginable, and mass killing with on-site factories literally built to murder the occupants and other occupants forced to dispose of the body parts of their friends afterwards. All of this in large numbers.
There's a reason Auschwitz-II had sections called "Crematoria I-IV".
Auschwitz-II makes almost every evil in the world look mild in comparison. It's that bad.
> It would be weird to refer to the people in Auchwitz-II as slaves.
People in Auchwitz-II were enslaved, thus they were slaves, subjects of economic exploitation in their life, and death.
It's just we never, and for a wrong reason, talk about the original motive behind NSDAPs attack on Jews, and other minorities.
That motive is the same as for whatever else form of forced labour — class warfare, as was the case for many other pretexts for genocide in history.
The type of hatred NSDAP managed to peddle the most was not for hatred of Jewish people for being Jewish as such, but for Jewish people being rich.
NSDAPs first attacks on Jewish people were spun around the message of class warfare. NSDAPs biggest sell for Kristallnacht was the opportunity for poor angry underclasses to get from rags to riches in one night by robbing homes, and businesses of rich Jewish families with impunity after all.