Also, the tomato rating is just the percentage of positive reviews, not the degree of positivity. You'd have to look at the average rating (the small print below the tomatos score), and do so for the top critics only rather than all critics (which are closer to the critics Metacritic surveys). I believe this score is at a 7.8 currently on RT. Still higher than the 6.8 (or 68) score over at Metacritic, but the difference between 68 and 78 is obviously far less than the difference between 68 and 92.
Another factor is that Metacritic weighs the grades of more important/influential critics (though they won't reveal which ones weigh the most... but you can bet that A.O. Scott review was quite damaging), and that Metacritic assigns a numerical score to a review even if it's unscored/graded, something RottenTomatoes doesn't do. Which leads to some subjectivity as they are essentially guessing the score they think the critic would have gave it. It's why I think they underrated the Variety and Hollywood Reporter reviews, both of which read closer to a 90 than an 80 to me.