I'm not sure why CBS would do the book if it did not have some legitimacy in canon, yeah it can be written over onscreen, but why get a producer and writer for the show to write this if you didn't want to make it worth fans investment?
For the same reason they did every other Trek novel and reference book they've done over the past few decades: to make more money by selling merchandise associated with a popular series. They're not interested in continuity; that's the purview of the creators of the show. CBS is a business. They want to make a profit. And the market value of media tie-ins has never been dependent on their canon status. Some fans obsess about things like that, but most just want to see stories about the characters and ideas they enjoy, and don't worry so much about consistency. It's worth the fans' investment if it's enjoyable
. That's what this is all about. I'll never understand fans who treat this like they're studying for a test and have to get the right reference materials. It's not work, it's entertainment. It's about reading a book for enjoyment of its ideas. If another book offers an incompatible set of ideas, that doesn't have to detract from your enjoyment; on the contrary, it can add to it by offering another interesting variation on the theme.
Mr. Goodman offered one version of events surrounding the Romulan War and the Federation's founding; whereas Andy Mangels, Mike Martin, and I have been developing a separate and incompatible version of those events. And that's fine, because it gives readers options, lets them explore two different takes on the question. Just like DC and Pocket offered different versions of Kirk's first mission on the Enterprise
back in the '80s, or Pocket and IDW offered different versions of Khan's exile, or the like.