Correct, but consoles are very predictable and stable systems in terms of technical issues. PCs come in a wide variety of configurations so Blizzard works to provide the game to as many systems as possible.
The advantages of objects rendering in the gameplay are relatively limited. Another reason why pros typically run at low settings is to get the optimum input and FPS rates. For details on that, see my tech guide here:
In any case in the most strict sense, if you are looking to squeeze out every ounce of competitive advantage, its best to play on low settings.