Earlier quoted context omitted.
Interesting. I can't find a way to read "graded in the context of peers" that doesn't parse into exactly the same concept as "sort employees by performance". AFAIK, it's not something you can interpret as, those are literally synonyms. But well, stack ranking is not only about sorting (the name is a lie), it's about placing people in fixed sized cohorts. The real question is if there is a limitation on the number of…
The cohorts at Meta are not fixed size (at least not at the team level). You do get to see the average size of cohorts, and you will need to explain why your team doesn’t meet them - for example if the entire team project is going exceedingly well, or the team is really made out if a lot of extraordinarily talented people - then you can argue why you have more than the average rate of excellent rankings.
Anyway, even if it honestly for "extraordinarily talented" people, that's still stupid stack-ranking.