Nope...its definitely a placebo. There is only a really tiny amount on the low vehicle cam replay angle placed right next to one of your wheels but thats always been there since day 1 of replays getting implemented.
Believe me 100%...if there was any improvement...I would have made a song and dance about it lol cause up until now that
you mentioned it....I was prolly the only guy in the world to highlight this issue a number of times...like this post I made in March:
http://www.neogaf.com/forum/showpost.php?p=156404359&postcount=12735
When you create a game so incredible looking like Driveclub...it becomes too easy to spot "small" flaws and this particular problem I have sticks out like a sore thumb on replays. What makes it a bit annoying is that we've had good, convincing motion blur on car wheels/alloys on other racing games since 2 generations ago on PS2:
Gran Turismo 3: