Actually I'm not surprised for a different reason. Since those offenses are so explosive on their own and have the ability to score quickly, opposing offenses get more possessions of their own. The more possessions you have the greater the chance you'll come up with an explosive play of your own. Dallas is a ground and pound, chew up the clock offense so opposing offenses probably have fewer possessions than opponents of the Rams and Chiefs. Maybe an explosive play rate might be a good stat to look at to see where teams fall on either end.