Are the 3D rendering methods behind Blockscape, minecraft, & cubeworld

All have a LOT of polygons rendered, more so than average games. Yet the game runs perfectly smoothly (so it seems). I suppose that this is because rendering the world is easier because the rigid block like environments are easier to manage because what should be displayed is more "predictable" and the computer doesn't have to accommodate for objects that can be in more flexible locations.

Thanks for any help!