I've read numerous forum posts on other sites where people claim this, but I've never seen anything officially stating this, or even a logical explanation as to why. I can't say I've noticed any differences across any of my systems, including one that went from Vista x86 to Windows 7 x64.
To be fair, I've also read numerous forum posts and websites proclaiming that aliens exist and are walking among us as well, but haven't given any proof either. I don't typically buy anything I read as fact, especially in a forum. Maybe this is, who knows, but it wasn't the case with Vista, and hasn't been the case in my own systems.