It’s definitely happened before, though I couldn’t say to what extent. The reason has been that if they rate games from major developers too poorly they stop getting access to their new games before release.

I care very little about critics these days though, and it’s mostly for the reason you suggest, differing opinions. If they don’t like the same types of games I like, what good is their rating to me? I’m not taking the time to try to find a critic that has similar tastes as me.