You may have missed the "multi threaded vs single threaded" section where they talk about a very similar pattern:

"The way it works is simple, it uses blocking IO, but each blocking call is made in its own thread. Now depending on the implementation, it either takes a callback, or uses a polling model, like returning a Future."

It is very relevant. Both async io and multithreaded io are ways to extract parallelism. Which one is more appropriate depends on the characteristics of the problem.