Bioware said the PS3 version would be the definitive version. Obviously it's the 360/PC versions that are non-cannon. 
Anyhoo, this is my theory: MS is the publisher of ME1, therefore MS has some rights to the ME1 story as well as the game. In negotiating ME2 port to PS3 EA had to agree to change or omit parts of ME1 from the interactive comic so that there were material differences from the ME1 story. Or EA's lawyers told EA that if they had exactly the same story for the interactive comic then MS might try to sue, hence they figured out how much they needed to change to make it hard for MS to throw a wobbly and sue. End result: fanboys crying about changes, EA minimises the chance of litigation.
For me it matters not, as I've not experienced ME1 so the interactive comic that comes with ME2 will be the story I know.
“The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt.” - Bertrand Russell
"When the power of love overcomes the love of power, the world will know peace."
Jimi Hendrix
