Well you seem to assume that Polyphony hasn't been working on a new damage engine during the whole time of GT5 development. I've seen many PC games have extra files left in by the developers who obviously didn't have time to add a feature in the final product. Gt4 was suppose to have online multiplayer yet it was dropped for example.
Thus as far as we know this new damage engine could have been worked on since Gt4 yet now after seeing Forza 3 they decided to fully develop it for GT5. (this is the same as saying Sony wand is copying Nintendo when Sony was working on stuff like motion controls during PS2 years)
Also the comment that Froza is "based on Mclarens billion dollar simulation" is about as much impressing to me as these so called "based on a true story" movies. I learn these movies often are a load of crap with just a hint of facts in them. So I guess this makes Forza 3 not a racing sim after all but a "racing sim" sim.
