I'm gonna say it: From my experience, most people who go on PIP deserve it. Amazon's been slipping the bar and they hire a lot of people who clearly are underperforming.
Doesn’t help that it’s extremely easy for new grads to cheat on their interview. The new grad hiring process has been such that you only need to solve an online assessment. If you do very well(all tests pass and it’s optimized) and then you do a 30 min. interview to explain the code you wrote. Copying solutions, changing variable names and just reading the code in the 30 min interview has anecdotally worked for several people.
It's not the simple. Sure Amazon has a bunch of no-talent garbage engineers (typically driven by SDMs who have been ordered to hire at any cost and BRs that either aren't strong enough to argue against the SDM or have likewise been told to pump conversions -- there are tons of loops that don't even have a BR interviewing), but some orgs are actually good at hiring and only hire talent. Applying URA at a director-level is injust and there is no cross-VP-org calibration that happens. While I agree that the URA target is likely lower than it should be for how bad some of the hires have been (e.g. L5s who refuse to use the command line for anything and have never written a test), there needs to be a better mechanism for identifying who is actually below bar.
Like these people are really underperforming, e.g. couldn't even design a basic system and defend themselves in a design review. Would barely write code and are slipping by. It's quite common at Amazon.