My understanding is that the RPG is very thoroughly researched to make it contain only the most accurate information. I don't think that Jim himself has fact checked every stat block though, and the refresh listings of various creatures aren't necessarily accurate (the senior council, for example, is pretty severely underestimated in their entries). Fred Hicks (the guy that made the game) is pretty good friends with Jim, so you can trust that he has his information correct, and I think Priscilla, goddess of Dresden trivia, fact checked the information.