>>715984557
when the game renders to your screen it is calculating and transforming 3D objects (meshes made up of triangles) to a 2D space (your screen) -- when it "rasterizes" it assigns the pixels on your screen to these 3D triangles. Naturally, the raw edges of pixels do not translate 1:1 to the sides of a triangle and so a lot of the GPU's calculations goes into defining essentially how much of an influence that triangle has on that pixel when applying shaders later on in the pipeline.

Basically, if there are larger triangles on the screen, your GPU doesn't have to focus on calculating multiple edges