Task.Wait() is just using the normal "thread" (in the way the author defines it later) blocking logic to do that in said case but I think the author is trying to talk about pure async/await approaches there as an example of why you still want exactly that kind of non-async "thread" blocking to fall back on for differently colored functions.

Task.WhenAny() is similar to Promise.any()/Promise.race(). I'm not sure this is where the author is focusing attention on though. Regardless if your execution is able to move on and out of that scope those other promises may still never finish or get cleaned up.