Cryengine does some funky stuff in regards to CPU performance, If you go into the game directory there's actually a .cmd file to start a second CPU benchmark set in the later snow levels that's pure explosions and physics, It RAPES CPU's... Dropping the GPU setting didn't help my Phenom 2 at all.
And of course it will drop in the actual game, If you can manage 60fps as a minimum in a fly through with no AI, Particles, Explosions and physics running on the CPU do you really think you can still do that in the actually game with all the above things placing strain on the CPU?
Yeah I know what benchmark you're talking about, but I've never seen anything like that in the actual game.
I'm still thinking that it's the rendering which eats up most of the CPU in Crysis.