..And that 2K is MINIMUM optimial size - the bigger the better of course. It's always beneficial to build very large polygroups that use the same surface because modern HW likes to render large amount of similar things... doing lot of small batches makes them stall and not hit their best performance. All this within reason of course, beacuse breaking meshes to smaller pieces will speed up rendering throug object culling. It's quite tricky to do "optimized" 3D beacuse the optimum case is a result of so many variables.
And the batch size thing comes from the HW manufacturers who have been optimizing their HW for years for large poly batches ("our blaablaa can render quantizillionpolygons per cycle"). Also modern games DO have ridiculous amount of polygons to render, one character is easily between 5000 - 10000 polgons, and this has additional with specular and bump maps etc which of course multiply the rendering work (multiple render passes).
And the batch size thing comes from the HW manufacturers who have been optimizing their HW for years for large poly batches ("our blaablaa can render quantizillionpolygons per cycle"). Also modern games DO have ridiculous amount of polygons to render, one character is easily between 5000 - 10000 polgons, and this has additional with specular and bump maps etc which of course multiply the rendering work (multiple render passes).