I only read through the article once, and fast, but it does seem to imply that night owl equals not enough sleep. That, and the amount of participants in the test seemed a bit too low for a true statistical overview.

I'm a night owl, always have been, even after I had kids. Go to bed at 1am-2am and wake up 7:30-8:30 depending on schedule. Weekends all bets are off. Works well for me, but that's the thing: I don't think we're all that similar. Different patterns for different people.