I love Football Outsiders. Without them, there would be almost no analytics worth anything regarding football, and every stats-minded football fan owes them a debt of gratitude.
That said, they’re not perfect, and occasionally they put something out there that just isn’t a good idea. I remember a few years ago they decided to write this: the Secret Sauce. The “Secret Sauce” stat was initially a Baseball Prospectus staple for a few years, originally created by Nate Silver; however, at some point they realized it didn’t work and retired it.
As it turns out, playoff performance, especially in football, is too small of a sample, and too matchup dependent, for any real trends to develop.