Because it just does dude. I don't know if it threads badly due to Windows or what but I was able to beat my own 8 core Xeon with a FX 8320 by clocking it.
Its just does! Lol I was expecting an answer like that. I'm generally curious though. Its just something that intrigued me when I was running the benchmark on all of my clients servers.
Make sure you are running the lastest R15 version and the bios and everything else is updated. Just to rule out any software issues and see if it improves anything at all