I don't play on DirectX 11 so can't compare (a bug that caused the game to freeze whenever I set up a game or used the Civilopedia - since it's always at the same point every time, it seems more likely a bug than a memory issue, but I've no idea if it was fixed in G&K). However, from the images most of these (except the black areas on hills, and the desert hill image) look as though they're intentional additional detail, such as snow on hills surrounding mountains or rocky hills topped by grassland - the seams look too continuous and integrated with the rest of the graphic to be bugs.