I see what you’re saying. For your bench mark code, it doesn’t look like you’re using a generator? How does the await compare to a generator? I only ask because the non-async example looks like there are a million ways the runtime could optimize it that might not apply in practice. (I’m on my phone now, otherwise I would try it).
OP's technique is useful for a consumer of a another function, to consume it in a synchronity-agnostic manner. In the implementation of the function consumer, you should find the usage of OP's technique.
In other words, this technique allows a library's implementation and interface to be synchronity-agnostic, but it does not say anything about the library user. If the library user likewise makes use of the OP technique, the library user code will remain synchronity-agnostic, otherwise it will be tied to be either synchronous or be asynchronous (parametrised to the synchronity).
