Companies rarely contribute back except for very few projects like gcc and LLVM.
FAANG does hire OSS devs, but a lot of them don't really do that much apart from being excellent politicians. To be fair, they don't get any time for OSS development in the first place.
However, they do have time for politics and often ruin the projects. People play along because they want to get hired at GNAAF.
As a result, these projects combine the worst of corporate and OSS development (horrible atmosphere and yet no money for development).