It's not about that. It's about 10 different clients all having their connections handled at the same time. There exist mechanisms to do that without async, and this post demonstrates that often they give better results.
If one connection needs to do a lot of work (your 10 queries), then that's a different (also important) problem to solve. Async is a nice (from a programmer point of view) way of doing it.
Now yield all those calls asynchronously as an array. What is this even about?