You misunderstood my question.
It seems to me that it is meaningless for a game to claim to support Dolby Digital. ALL modern games output multi-channel audio. Dolby Digital is simply a compression scheme for multi-channel audio that was developed because films and or DVDs don't have enough data capacity to hold all of the audio streams for a movie in uncompressed form. Compressed or uncompressed audio has nothing to do with the game. Thus, since ANY modern game can claim to support Dolby Digital (by sending DirectSound3D to 5.1 channels and then encoding it through Soundstorm), why does FarCry make the claim while others don't? The only thing I can think of is that perhaps all of FarCry's sound output falls under the 17KHz level. If you don't already know, XBOX and Soundstorm real-time DD compression cuts off frequencies above 17KHz. I suppose you could argue that if a game outputs any sound (screams, squeals, beeps, etc.) above that frequency, it will be cut off by the DD encoding and it technically won't sound as orignially intended. Nevermind the fact that neither is the compression totally lossless for frequencies below 17KHz, its just hard to notice the loss in quality.
Saying "PC game X supports Dolby Digital!" is like saying "Music stored on CD Y can be converted to MP3!".