Windows has its own fibers facility which does some things for you but still leaves the scheduling to the application so it's still fibers. It's a little confus

Windows has its own fibers facility which does some things for you but still leaves the scheduling to the application so it's still fibers. It's a little confusing in the article but they look at the Windows API as a kind of API template - what do you need to implement to have fibers. Then they describe their own implementation.