I really don't think its rendering "all that much more stuff". It seems like its the same as cranking up the FOV? Which normally doesn't effect what is being rendered or the frame rate. Engines don't always actively check and cull objects that you aren't directly looking at, maybe with some things, but too much checking…
I don't know if its really the same effect. TV manufactures seemed to think light leaking out the back of your TV was a cool feature, but this is actually projecting things on the walls and surface not just colors. the snow effect in the cartoon-ish racing game, simple yet pretty cool, the same could be done with rain or…