Or it's too good at being a PIP ;)

Many PIPs (in my experience: most PIPs) are not good faith attempts to allow a poorly-performing employee to improve. The decision to fire them was made before the PIP was issued, the PIP is just documentation to protect the company in the case of a lawsuit.

Amazon's approach here - if correctly reported - seems like it takes the step of embracing a PIP for what it actually is, by making it purely a documentation/justification task and eschewing the (often make-believe) step of letting employees fulfill the requirements of the PIP.

Overall I'm very much against non-transparent PIPs. Short of gross behavior, employees deserve to know if they are going to be let go for performance and prepare an exit plan. Not to mention PIPs are often arbitrary and capricious - not every employee on a PIP is actually poorly-performing. At the very least it gives people time to jump ship.