Well, duh! I don't understand why Crysis won't have the same physics in multiplayer mode running under DirectX 9 as it does under DirectX 10.
Yet, so many people don't stop there and try an learn, but instead try and explain it away, with their admitted lack of understanding and limited scope on the subject.
I'm sure plenty of people had great arguments on why the earth was flat, because afterall, it was all they could see.
I'm just saying more may meet the eye, and we should possibly consider that maybe Crytek is leveraging things in the DX10 API for once that can't be done in DX9, therefore they are not compatible. This compatibility would be the issue for any developer that leveraged DX10 in changing the game world, beyond the cursory junk they have called DX10 thus far.