When you have one type of grass but cut it at different heights (ie fairway and rough) it looks unnatural and, depending on the proportion/ratio of fairway to rough, un-architectural too. But when you cut the grass at one height everywhere, it looks both more natural and more architectural. Strange, since all grass and any mowed grass of whatever height is all put there and tended by human hands, so it should all look equally fake no matter what. But there is something about matching the uniformity of one type of grass with the uniformity of one cutting height that seems to help hold the con/help me suspend my disbelief. If you have different grasses/textures (eg bent, heather, fescue), anything goes, ie you don't need uniformity in heights (and in fact, you want the opposite). But if there is only one type of grass, it looks better and more real and more golfy if its all at the same height.
Peter