Not true from what I can tell. I was fixed by this idea some months ago and did some prototypes. I did the straight approach and rendered a map of 256 x 256 tiles without any problems. For some of the tiles I even used 2 entities, namely for the lava and water tiles. The engine was running fine even when showing all 65.000 entities. With fogging enabed and a smaller clip range it ran perfectly fine, i.e. always > 100 fps.