I am guessing the review sample is a ES spin, so final could have higher clocks, and as well increased memory clocks as AMD have mentioned.
Considering this is almost hand in hand with titan at 800Mhz, 1Ghz would would provide somewhere around 20% more performance depending on achievable memory speeds.
27% increase in SP count but W1zz's benchmarks of Titan VS 7970 shows the AMD only 12% slower at that resolution, so either the card is crippled and someone got it for other testing, or they have failed to reach their target.
A efficiency improvement in the 7970 for higher core speeds and better memory would have been a better investment for them if this were true. I doubt this to be true, instead its most likely a crippled ES card.
http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_Titan/22.html
http://tpucdn.com/reviews/NVIDIA/GeForce_GTX_Titan/images/skyrim_5760_1080.gif
Or its meant to show the validity of the core architecture at the same speed as Titan, while consuming less power, and having more features possibly.