What does "insular and unhistorical bias" mean?

This is for my english essay, I am writing a research essay to prove that A Tale of Two Cities by Charles Dickens is a historical fiction novel. I looked up A Tale of Two Cities in The Encyclopedia Britannica and found a quote that goes like this "...The insular and unhistorical bias of A Tale of Two Cities..." I was just wondering if anyone knows what exactly this means so that I can use it in my essay. I'm pretty sure it means that Charles Dickens wasn't biased in A Tale of Two Cities because he was not living at the time of the French Revolution and got all of his information from strict research. I just want to make sure that this is right, or else my essay may not be as strong if my quote doesn't back up what I say in my essay!