For one, I thought this was published by EA, not Microsoft. So unless there's some conspiracy theory about DX10 I'm not understanding the connection here.
But I'd rather here from a programmer that has coded for both DX9 and 10 and hear their opinions. It's quite possible that it's easier to program physics and day/night cycles in DX10 than DX9, but I'm not sure. Perhaps their using the extra GPU power of the 8800 cards to process physics, I don't know.
I'd like to hear some cold hard facts on the matter before jumping to the conclusion that it's all just collusion between Crytek and MS trying to force us all to buy better hardware and newer operating systems.