I read the abstract, pretty interesting. I did a word search for "wake" looking for if they talked at all about early waking times being correlated with overall regularity, as that has been my personal experience. Unfortunately they didn't talk about it, or if they did I couldn't find it.
I am also curious about this. The best sleep I ever had was when I was teaching an early morning class. Part of my morning routine is a short run, so this meant I was regularly waking up at 5am. I fell asleep regularly at 9pm when I was on this schedule. I use a sleep band [1] to track sleep, and it was the only time when I've been able to consistently get "high scores" on it.