Folks, Optimum is talking about 2560x, max DirectX 11 game settings with full-res fullscreen effects, DirectX 11 object and environment tessellation, 2048x2048 textures, and hardware PhysX effects.
The game is highly optimized, allowing 4A to run all that stuff simultaneously at such a high resolution on one TITAN, two 670s, two 680s, or one 690. If it weren't optimized this would be impossible.