I understand that the holes in the exhaust are to cool off the exhaust during the regeneration but is it really that important to have cooler exhaust for those 2 inches behind the hole?

 

Its more important that pedestrians and cars along that side of the truck dont get toasty so thats why they have those tips so the temps are not so high at the exit point. I beleave the rest of the exhaust has alot of heat shielding to protect the truck.