The ducting coming out of the sides is just so it's easier to route isn't it? To me it looks like it only there because it's not obstructed by the engine that way (that's what the OP said isn't it?)
From what I've learned off this forum it only takes an opening with the area of 1/4 of the heat exchanger's surface to keep it working efficiently (at speed, 1/3 for a car that sits in traffic) and that the exit opening needs to be about 3 times as big as the opening (I hope i have that right.) In my head it seems that it would be easier to get the 3 times larger opening (if you have a blocked off grill) by doing it because you can put some long, wide vents in the sides of the hood and since the L-series is so narrow making the ducting shouldn't be THAT hard...Thats all in theory of a 20 year old mind working off of absolutely no sleep.
On a side note, I love looking at rally cars. I don't know why but to me they just look brutal. F1 and cars like that Corvette posted above are more...finesse looking.