Nah that's just laziness.
If you look at Just Cause 2 the PS3 version is once again the definitive version because it includes the youtube recording feature, for me that's the selling point of the game, and as a reviewer that'd earn it at least another 10 in the 10/100 scale.
However IGN gave both the 360 and PS3 versions 8.8. Which is a fine score, but isn't exactly doing the PS3 version justice.
They are bias in one respect though. I believe IGN do exclusive content for the 360, which is distributed directly onto the 360. Last I went on my 360 that's what I remember, they dispensed game tips and other crap. Odd these aren't also on PS3, I'd guess Microsoft pays for them?