Well I think the Bulwark, Dauntless, Liberator, CC-7700, CC-9600, ... were just made up for Rebellion. The CC-7700 was later used in a book by Bel Iblis against Daala, so it has been officially sanctioned, I guess. But the whole idea about the being made up has a flaw: Where exactly do we draw the line ? If we draw it after the movies, then there'll be no Thrawn, no Yuuzhan Vong, no Jedi Academy, ... well, you get my point. So, my view is this: these officially sanctioned ideas are 'real' in the StarWars universe. Although I would've liked to have a Dauntless or Bulwark mentioned in the books. The way its there, you could think the whole Alliance/NR fleet consists of MonCal ships, frigates, corvettes and gunboats. A bit more diversity would benefit the whole story, I think. It's a big universe after all, so there is likely to be a vast number of different ships as well, although the Empire kept surpressing all the aliens.