Haha, well investigated - did you also take a 6 year hiatus?
Civilization departs so much from history, not just in what happens, but also in its fundamental mechanics, that talking about realism or historical accuracy makes no sense to me.
Being historically flavoured is the closest that Civilization comes to history. This flavour is vitally important to Civilization games, and is definitely changed by civ-swapping. But its impact is almost completely unrelated to questions of accuracy, because there is virtually none to speak of in the game anyway. Whether you like the new flavours or not is completely subjective, so there's nothing worth arguing about here.