I visited Auschwitz this summer and something surprised me. In the original Auschwitz camp was a prison (a prison inside a prison). The prison was used for several things, one of them being a place to punish Jews, Roma etc who where forced to work. For example, our guide told that when a labourer peed without permission he could be punished. The prison contained, among other things, a starvation cell, sufication cell and standing cell as means of punishment.
I also learned that pretty much 75% of the prisoners that arrived where immidiatly exterminated. Punishment is a way to correct someone's behaviour. So my question is; Why would the SS take the time to correct a labourer instead of executing him and replacing him? It seems odd to want to punish and correct the behaviour of someone who you will execute a few months later anyway.
One of the reasons would be that those sidelined for work were most likely a source of money to the SS and therefore assets; most labour workers were leased out to production plants nearby the camp for a fee, but had to be fit to work. And as the people coming of the trains to the camps were in mostly terrible condition due to the horrific nature of the transportation, healthy workers were few and far between. As a result, the SS guards couldn't brandish death as a threat to the workers but could still use the methods you have mentioned (even if these brutal treatments resulted in death). Eventually though, as you have mentioned, the workers were worked to death or gassed, for the period they were useful and profitable they would be punished not killed.