I normally look at maps in books very closely ^^ So yes, I did notice that. Why is this bugging you? Because it's hard to do in digital mapping or because you think that it is not realistic?
Of course I don't know what the thought process of Erikson and Esslemont was ... but them being archaeologists and anthropologists, I'd think that they know about such things. Then again, it's a fantasy world and there could be supernatural/magical reasons for stuff that "makes no sense". For example there are some glaciers in the malazan world that make no realistic sense...but as the Jaghut are masters of the warren of elder ice (aka Omtose Phellack), they can do things not possible in reality

Not sure if that helped ^^