Yeah, I agree that's an area that needs work. I admit I didn't bother to read every word, but I did search for "async" to see if he mentions aio(7) to complain about it and I saw that he didn't.
Don't get me wrong, there are lots of room for improvements in POSIX IO interfaces. For example, POSIX doesn't define any modern event systems (epoll, kqueue, etc). But what's the result? We use libevent/libev.
This sort of seems like the result he's asking for in diverging from POSIX, which we ... already have. There are a lot of pretty great non-posix standard interfaces available too!