> The real win isn't spawning a massive number of threads, but automatically yielding on network I/O

This is of course what normal OS threads do as well, they get suspended when blocking on IO. Which is why 100k OS threads doing IO works fine too.

Yes. What I was trying to imply is that now there is a lightweight processing unit that still is able to suspend on IO (independently and without involvement from the OS scheduler), but can do that without relying on async/reactive patterns on code level. This required significant changes to the standard lib and runtime.