The first problem with this logic is that there's no such thing as a plot hole. Every time an inconsistency arises, you assume that an explanation must exist, and has in fact been "spoon-fed" to us, or else the inconsistency wouldn't be so obvious. But you never consider the possibility that an inconsistency may actually exist. Nor do you really put much effort into trying to demonstrate where the authors offered specific evidence that would eliminate a seeming inconsistency. The second problem with your logic is that it cuts both ways. How come no one is surprised that he doesn't look like the classical image? If a shot, obese, Chinese man with dreadlocks turned out to be Abraham Lincoln, people would express a bit of surprise it wasn't the towering, marfanoid white man with a stovepipe that every portrait said he was. Likewise, I think people would be taken aback if someone who looked like the Elephant Man claimed he was actually Napoleon Bonaparte. Therefore, the fact that no one was surprised by Khan's appearance shows that he was always supposed to be a pale British man.