Just like SWFD, RR receives technical data from many different sources, including those who actually work the systems we monitor. As pointed out in an earlier post, information on useage can and does change form time to time, for any number of reasons. Some of these changes are permanent, but some are only temporary. Of course, once a book goes to print, it can not be changed, so SWFD accounts for updates, by allowing the purchaser of the book to access a passworded online site to see if any changes have occured since the book was published. Again, these updates come from listeners and techs.
RR is a little more fluid. The information on this site can be immediately updated to reflect changes in the radio environment, assuming someone submits the changes to RR for updating. If no one has submitted information that has been personally verified, then you might not see the information on RR, even though it might be published in someone's book.
Both have excellent aspects, which is why I not only check RR, but I also own the SWFD books. They are nice compliments to each other.