Lol.

just implement threads again, with basically the same semantics, except that they are scheduled in userspace

To be fair, the Go implementation here is quite interesting since it scales way better than OS threads, so there are fewer downsides to spinning up a ton of threads. So it's closer to async abstracted behind a threading veneer, like the GREEN functions in the article.

Though the "known only to you" criticisms are absolutely on-point.