Have you heard of hire to fire? When there's an incentive to game a metric, the metric gets gamed.
Also, because each hire costs thousands of dollars, the company is literally wasting millions each year because Bezos had this dangerously ignorant and dehumanizing idea that people - except himself of course - are lazy so they need to be terrorized into being productive by firing a certain percentage of the employees.
Ultimately, it damages not just Amazon's brand as a employer, it reflects poorly on Amazon employees and managers for going along with this charade.
Wouldn't the most valued people get retained at the end, whether the new hires were "hired to fire"? If so, a manager has no incentive to do bad hires.
I fail to understand how people do not see how this simple metric can be gamed. Am I the only person thinking in those weird terms imposed by the system?