I disagree with both elements of this premise: 1) that Amazon is cruel, and 2) that the objectives are achievable by other means.
Performance, as I say above, is the point. Amazon pushes very hard for performance. Achieving high performance is difficult and uncomfortable. But to classify the activities which yield high performance as "cruel" is an interpretation. This article and the NYT articles it cites bend over backwards to paint Amazon in a negative light in this respect. But here's' the thing, Amazon is very transparent about both their aims and means. Amazon encourages and incentives workers to quit bc Bezos (quite correctly, in my opinion) recognizes the "march to mediocrity" as a basic reality of large orgs. Amazon offers training which will help employees find different jobs and pays quit bonuses. Flat out: that's not cruelty. It is actually a fairly humane and "progressive" approach to a difficult and uncomfortable challenge.
Implicit in these claims is of course (the fairly absurd, in my opinion) belief that there are some more effective means of achieving sustained and very high performance that are more comfortable for employees. This, to me, is the root flaw in the "cruelty" interpretation. It basically requires us to be believe that Amazon is run by sadistic people that are aware of better means by which to achieve sustained high performance, but that they choose more uncomfortable, "less humane" options instead. If I'm wrong, I simply ask that the people on the other side of the argument point to proven methods (that they interpret as not cruel) which yield the kind of sustained high performance that Amazon has achieved.