alt Hacker NewsPart of that is the assumption that Amazon/Meta/Google all have dedicated engineers who should be doing nothing but tuning performance for 0.0001% efficiency gains. At the scale of millions of servers, those tweaks add up to real dollar savings, and I suspect little of how they run is stock.
This is really just an example of survivorship bias and the power of Valve's good brand value. Big tech does in fact employ plenty of people working on the kernel to make 0.1% efficiency gains (for the reason you state), it's just not posted on HN. Someone would have found this eventually if not Valve.
And the people at FB who worked to integrate Valve's work into the backend and test it and measure the gains are the same people who go looking for these kernel perf improvements all day.