yes, it's appears to be for show, like many cars with hood scoops, brake vents, etc.
http://forums.subdriven.com/zerothre...4096503&page=1 - lambo, r8, bugatti
http://www.m3post.com/forums/showthread.php?t=237342 - m3
http://www.cartype.com/pages/2742/just_venting - sti
btw, in real life you can't put your hand through like that. that was a pre-production vehicle. and they're not really exhaust tips... it's called diffusers and it basically protects the bumper from heat damage, reduces backpressure, and reduces backflow for speeds >100mph which eliminates rear end lift, which was needed with a top speed of 170mph.
http://en.wikipedia.org/wiki/Diffuser_(automotive)
but borla finally released a cat back system with 4 outlets (instead of the oem of 2) for the stock tips, the only issue is that borla had fitment issues with the is350's - not sure if many isf's owners will jump on it.
http://www.borla.com/products/new_products.aspx