The worst part is you can be a top performer and still be low-ranked because you have a poor manager or because they want to target a specific metric that doesn't apply to you.

The whole thing is almost always used to perform shadow layoffs: Basically a way to target a group you want to layoff, but then fire them "for cause" of low performance based on measures that may have little to do with their job. I had this happen to me at Yahoo after Melissa Meyer took over (another toxic billionaire that shouldn't run a company). I was a senior software developer, and was always a "top performer" in yearly reviews and raises, which meant after a few years I was very expensive. They introduced stack ranking and, while I knew what it was, I wasn't particularly worried as I was always ranking at the top. Then, a month before the reviews and ranking, two of us that were both "expensive" and over 40 were suddenly re-organized under a manager who managed a QA team, and we were then stack ranked against QA engineers based on QA metrics, which are very different from those used for software developers. Even though our reviews were also fantastic, we both fell in the bottom of the QA rankings because we weren't assigned to do QA work. Within a month we were both let go "for cause". As I still knew people there, I found out they repeated started doing ranking every quarter and repeated this process with a few different people each time, always using the same manager (fuck you Brad, you enablist PoS).

That's a classic example of how to use stack ranking to target older and more expensive employees and to get away with not having to do expensive layoffs and severance packages. Incidentally, it isn't always entirely legal: https://www.shrm.org/resourcesandtools/legal-and-compliance/employment-law/pages/yahoo-forced-ranking.aspx