It doesn't seem to be an LOD issue. It stays the same no matter how long you stay in the area. I flew from Chicago O'Hare International Airport and did not change from arrival on approach, and if there is any impact, I think it is the GSX Mod.
Some of the objects do not sink and float upwards, probably due to the strange topography, when the expressway connecting South Terminal A and North Terminal crosses the 9L-27R runway on the way. (Near Taxiway G)