You very obviously have a point here. If you could play the postseason scenario out 1000 times would the Rams win the Superbowl every time, of course not. Maybe they would win with the highest frequency, maybe not.
Winning the Superbowl does not prove you are the best team. Again: winning the Superbowl does not prove you are the best team. It is a combination of skill and luck.
GunnerBill thinks like a coach and their job is to disregard luck because there's no value in thinking about that. Good coaches and players focus all their energy on the parts of it that are in their control.