What part of that sentence are you surprised by?
Divine Power gave us a lot of insight into the core world's mythology, including the rise of the Raven Queen. It revealed that she was once mortal, and overthrew Nerull. It probably also mentioned that she left Pluton to go to the Shadowfell, though I can't remember the details.
I can't find any Raven Queen article, but I'm pretty sure everything in that sentance was already known, or at least implied.
Which makes the Raven Queen one kickass character.It seems the Raven Queen is Unaligned simply because she found Evil inconvenient.
Didn't bits of this first appear in Manual of the Planes?
FWIW Scribble, I have these kinds of "canon-brain-farts" all the time. ...Probably because I'm not religious about keeping up with it, mind you.
I'm not too fond of the official storyline for the Raven Queen, which makes her more Evil than Unaligned. I have my own version, which has a more mythological approach.