@lhochstein "It's complicated"
Having been in Amazon, Google, MS, the Google process is (was!) a clear outlier, which was totally culturally aligned with how everything else in the company worked.
1) Designed to fail closed
2) Detail over big picture
3) Written over relationship
1) "Fail closed" -- jargon for "optimised to say no by default".
Many processes in Google were like this, probably the largest other one being the hiring process. (Many Googlers hated the hiring process since they felt it said no to people who would 100% have been great hires...
...sometimes being burned to the extent of refusing to do any more interviewing.)
But the promotion process is (was) the same way - if the committee couldn't convince itself the case was watertight, it wouldn't promote.
This obviously led to a situation where a lot of cases were refused and meant a lot of heartache and unnecessary departures, but also a situation where by god if you'd MADE that bar, it was close to undeniable.
There was a very strong shared sense of what each level meant.
Some more so than others: I think L5/Senior is probably the one most folks have the largest degree of precision on, and above that it's harder to tell. But one benefit was that title/grade inflation was very strongly counteracted by "the system".