I think it's premature to try to bring this to light. Since it occurs only on the gfFX5900 and gfFX5600, but not the gfFX5200, it might be cheating.
But B3D is not ready to come to such a conclusion without more testing. So you shouldn't jump to conclusions yet either.
Although it is interesting that Splinter Cell benchmarks jumped up with recent drivers, as did Shadermark results...I honestly wouldn't be surprised if nvidia was cheating.
P.S. I haven't read the thread today, just last night, so there may be new developments I missed. If so, just disregard my comments.