That blog slightly misrepresents futex. Or perhaps it's outdated. It's written as if futexes can only be used with a 1/0/negative protocol, but that's not true. The values used are up to user space.

Indeed, in another article Chen actually explicitly claims that msft invented (what we understand to be) futexes and that Linux switched their futex syscall from semaphores to futexes by copying windows. It is truly a wildly incorrect and implausible view of history.