It doesn't in rust but in many other languages there would have been a single blessed async library and trying to use anything else would have been very painful. The fact that rust doesn't particularly force the use of it's standard runtime is key to why rust is useful for kernel work.
Yeah, but I think what they're getting at is that Rust could provide a standard executor in the library and also be modular enough that you can use whichever one you want. The questions are orthogonal
