edit:
nevermind, resolved by running around and jumping

to the op: the mechanism you described is well known and doesnt have much to do with netcode. It is in fact one of the oldest issues with game engines like arma. Most folks believe that the GPU is the most important factor in rendering 3D scenes; they are wrong. The CPU needs to do most calculations, in fact, it is the CPU that continually checks and refreshes the positions of all the "points" in a 3d space which then forms up your "objects". The GPU task, is basically just to apply the texture to the objects that the CPU has drawn and moved. So the equation is very basic: the more objects appear on the scene, the more calculations the CPU has to do. More calculations means slower output from the CPU. And in fact, the GPU work is not increased much, since the textures which make up your scene are already stored in its memory. As you can see, this equals to a GPU that gets less work to perform, if the CPU is under load. Don't let others fool ya into thinking that netcode is responsible, this basic principle is as much as valid in single player games / apps