The entire NFL playoff system is a fraud. There is no real reason. Seattle was simply left out for convenience. Baseball would have an open revolt at such a nauseatingly cynical system. In football, offsides is five yards, holding is ten yards, a personal is fifteen yards.
Nobody really knows what pass interference is.
Part judgment, part acting, mostly accident. Baseball has no penalties at all. A home run is a home run. In football, on a score, you look for flags. Football acts can all be repealed.