I don't doubt there are low performers at FAANG. I just believe when you're doing a 10% layoff, there's no way you're not going to cut high performers as well. Some layoffs are just purely based upon the department level.
Sure, there will be some high performers that get caught in that 10% net. The F500 shops wants their recruiting teams looking for those candidates, but they need protect themselves from adverse selection. An ex-FAANG developer who thinks they're 10x and is given unconstrained runway to prove (or disprove) it can cause a lot of damage to an unprepared but otherwise functional team of 1xers.