Got the game a couple of days early so was wondering if anyone know the answer to this. I'm almost finished the story mode and I've watched all the cutscenes so far, but I have had to go back to previous chapters to complete the "missions" in each one. During these, I've skipped the cutscenes. Surely this shouldn't negate the achievement right? I'd hate to have to start all over again for a measly 20 points, and I have seen the cutscenes. Only when I see them again do I skip them. Anyone finished story mode to confirm this?
I had the exact same question... like you, I had to go back a couple of times to complete missed bonus missions. I'm guessing if the cut scenes were watched fully first time round we should be fine. Time will tell, I should have it done by the weekend.. Ill keep you posted.