I'm not sure how this applies to what I was saying at all, you're comparing hand optimized ASM code designed for a specific purpose to a general purpose operating system, there is no relevant comparison to be had they have nothing to do with each other. ...
Any code Linus Torvald wrote can still be improved by recoding it in ASM for the specific platform. ...
The only modern reboots to the OS so far have been IOS, Android, and Microsoft is starting to edge in slowly. They achieved this via a complete reset of the entire system. Going to be a rough next 10 years for software developers.