No it doesn't. Gamespy dont' know anything. nAo (ps2 programmer and now PS3 programmer, if you don't know him) ran the game on the Performance Analyser, and it's hovering on the 3M polygon per second figure.
But if you want to trust Gamespy, by all means go for it, doesn't change the reality of things.
16M is way over the top, if that's what they say, they really have no idea.
Besides, it's not like GT4 has "hundreds of cars looking perfect" on screen at once, like you say...
EDIT: Actually i have to admit, the conversation with Marco was long ago so my numbers could be off, but it's either 3M polys per second or 30,000 polys per frame (that's 1,800,000 polys per second at 60fps so that's actually worse) and i can't really remember if it was average figres or tops. I'm sure he can clarify, if he has time. Either way, 16M polys per second for GT4 is laughable.