[dwaite]

The devil's in the implementation details though. The operating system may provide both fully-preemptive threads on which to schedule user space cooperative threads (scheduling on system call). At that point green threads (e.g. threading implemented by a virtual machine on top of the operating system) do not provide the same value. This is actually why Green threads were effectively pulled out of Java for a few decades.

Fibers are distinct in that they have no scheduling and are code being run on a thread - if the thread is preempted, it will resume on that same thread. Unlike cooperative threading, they must explicitly yield.

Coroutines have such varying implementations that you would need to define requirements to know if they count as fibers or not - for instance, whether you mandate a C-compatible stack.