This is false. I'm friends with many people across many companies, and we all openly share salary information, including RSUs. The numbers are fairly close, there's no way it's off by half. The biggest difference is Netflix, I would have expected them to be higher. Their biggest difference is they pay cash, and the culture is either you fit in and are extremely happy, or you're terrified of getting fired and you are within less than 6 months.
This is the biggest difference between now and 15-20 years ago. Before it used to be a secret but now everyone shares the data.
Manager since when? Maybe 6+ years ago it could've been half.
I'm L5 and I earn 400k+ (I joined last year), the compensation on levels.fyi also lines up accurately to my company's compensation data group (in which individuals anonymously report their salary).
These compensations are also accurate to those reported on Blind (anonymous work discussion app) by hundreds of individuals.
I have many co-workers and friends, and know the soft max paybands of each level. The comp reported on levels.fyi is very accurate.
Might be the team or sub-org you were in. This data is also for fresh offers in 2019; most FAANG engineers who started prior to 2019 are earning less to much less than listed.