As they said, it comes from an old novel that was probably never in the main canon and now it's being made official. Why? Who knows. If it was Kurtzman or one of the new writers trying to put their personal stamp on something it would make sense. But to throw this bone to a writer from 40 years ago seems random.
Personally I don't think the book should have revealed it either. If it's unpronouncable then it should be unreadable too. But then they gave Uhura a first name even though Roddenberry said she only had one. But Nichelle Nichols embraced it, probably to please the fans.