I don't think that's really relevant to his point. His argument is about control flow, rather than capabilities. The library he has built is designed to provide

I don't think that's really relevant to his point. His argument is about control flow, rather than capabilities. The library he has built is designed to provide any functionality that didn't previously exist, but rather to make code that accomplishes the same tasks as before easier to reason about and somewhat safer to write. An implementation of this pattern could handle the spawning of functions however it wants and the language supports (as independent processes, threads, with an event loop, etc.).