Square Enix is responsible for the higher-pipeline functions of calling and rendering objects, like the buffalo, and it's not like GameWorks has the ability to reach outside of the world, grab assets, and force them into the game. We would put this squarely on Square Enix, for now, but nVidia does have some responsibility in getting the rest of their GameWorks features fully integrated and working (even if Square is ultimately coding it, nVidia has its name on the product).
What we do know is that the benchmark is unreliable, and we suggest not using it. Wait for our final launch benchmarks. This will take more time to research, but we will keep our eye on it and are in touch with the teams responsible for the game's graphics.
If you need more visual examples, check the accompanying video for this piece.