He's saying they save their best plays for the playoffs. They aren't putting anything new on tape during the regular season. Look at the last two Super Bowls. They won against Philly using a play they never ran before. Scored a TD, then flipped it and ran out of a different formation on the opposite side and scored again. THen, the next Super Bowl, they ran another variant of that play to score a TD against SF after not running it the entire season. They aren't putting that play on tape trying to score against the Panthers in the 2nd quarter of week 12. They run the same boring shit and if they don't get in, they take three points.
Now, the Chiefs have their problems, and can't do whatever they want, whenever they want, but if you think they aren't holding something back, you are mistaken. Reid is not MCDC, keeping the hammer down even when he's up 3 scores. And while MCDC's style is way more fun to watch, it's much less likely to win the SB.