This is crazy! I've never heard of DSPD before, but I've explained to my girlfriend several times (as recently as a couple weeks ago) that no matter what time I go to bed, I don't really fall into a deep sleep, or fall asleep at all, until around 4am. I'll either be fully awake tossing and turning or I'll have a really light sleep. I'll wake up by myself around 11:30 or noon.

I have the same guilt about it as you do, and I'm a total baby about being woken up early. It's been this way my whole life.