The SS officers view the inmates as subhuman and their only value is in physical ability/health.
In the passage, it is understood that life or death depends on the level to which doctors of the SS consider the captives as physically appropiate to stay as useful workers. Here, the head of the block recommends the prisoners to follow some steps so SS doctors are convinced that they can be selected.
yes, it would have a slight difference because you would have a lot friendly chat with your friends than your grandparents because we show respect for elders. modify this answer! :)
