> Is that specific to Linux?

I don't think their point was about knowing the stack, but being able to point a harness at something running on your desktop GUI and say "change this".

Being able to edit and recompile pretty much any part of the OS and userland (often not even needing to reboot!) is not something that can be said about Windows for sure, or even lots of things on Macs too. Or even when the browser is effectively the operating system, the JS/TS others write is also hard to change in your end.