[Perfect Stu]

the reason why IGN uses a "not an average" system is to prevent themselves from forcing a score down because lack of multiplayer, lack of this, poor this, etc.

unless the reviewer said "the game would have scored a 9.9 if it had better multiplayer", I think it would be unfair to assume, as Link did, that they deducted tenths of a score directly in relation to their assessment of the multiplayer aspect.