Beyond Birthday Because several people on this site are fucking stupid and don't understand how the rating system works. They rate based on the cover/summary or even the publication date.
Thomas Don't blame the reviewers/raters. Blame goodreads for even allowing people to comment on unreleased books.
Trevor Sherman I do book reviews and have received ARC's as early as 7 months before a release date of a book. I am not saying that is the case here and I know its not for Rothfus but that is a way you will see some books rated and reviewed before a book is out.
Misty People also write critical reviews before the book is released if they're pissed at the author. This site could be useful, but it's too lightly monitored. There should be no reviews posted until much, much closer to the publication date.