In many cases the lib will rely on threads to handle calls to synchronous functions, got me wondering if there's a valid use case for running multiple async threads on a single core.
Eg in a user application you might have the performance sensitive work (eg rendering) which needs to be highly parallel - give it a bunch of threads. However when drawing the UI, handing user input, etc you usually don't need high throughput - use only 1 thread to minimise the impact on the rendering threads
In my work with server side code, I use multiple async runtimes. One runtime is multithreaded and handles all the real traffic. One runtime is singlethreaded and handles management operations such as dispatching metrics and logs or garbage collecting our caches