The notion that any type of consistent "bar" exists for hiring at FAANGs is a myth. These companies are far too large to consistently apply hiring standards. Some teams intentionally have different standards, some teams unintentionally (due to the hiring managers or interviewers just not being on the same page) have different standards, even within their specific team. Some teams are so desperate for people that they'll hire anyone with a pulse, while others are so flooded with applicants that they don't hire anyone unless you have 6 PhDs and won a nobel prize.
At my FAANG, it's so well known that the "hiring bar" is bullshit that when someone wants to do a team transfer, we usually require them to go through a full hiring loop again, just like an external hire, because there are some teams/organizations within my company that we do not trust to have upheld a reasonable bar when initially hiring someone.
For what it’s worth, the process is becoming standardized at the L5 Industry hire level at Amazon as it was for most L4 new grads. The hiring bar being different across orgs is going away soon.
Anecdotally, a lot of engineers (and especially managers) have this mentality where they don't treat the job as something that puts food on table and helps the company move their products forward in what ever pace the overall organisation is happy with. They want to get the high of entire life's achievement there which results in dissatisfaction/burnout.