I don't know. I have seen the same tests and was never sure why I was able to get playable framerates at 1600X. Just a few days ago I applied the mod everyone has been using and it didn't give me any better frame rates, but it did add some graphical enhancements to the water that were beautiful. From what I understand, some of the DX10 setting were disabled in Crysis even for the highest settings and the mod adds them back. Some people are reporting much better frame rates with the mod though.
I have to run to a meeting , but when I get home later I will fire up crysis and double check all my settings to make certain I am not overlooking something, which if enabled, would slow down my framerates, since to be honest, I just went through the settings when I first installed it, set everything to highest including AA, and then started dropping the resolution until I got to a playable setting.
I will report back later.