OK, but there really are a lot of guys who win when it matters.
Brady, Flacco, Roethlisberger, Manning's, Brees, Rodgers, Wilson.
That's 25% of last years starting QBs who have all hoisted Lombardi's and have had previous success in the postseason.
And THEN, you start looking at other successful postseason QBs who haven't won a SB, like Rivers and Luck. Heck, even Kaepernick has four postseason wins.
You're looking at 8-10 QBs in this league right now who have proven they can win consistently in the postseason. And that's just QBs... that's not even including every other position on the field.
Hence why this notion of being a "winner" isn't nearly as rare as people make it out to be.
Maybe the best way to look at this is based on opposing team perception before a game. I worry more before a game against the Brady, Rodgers, Wilson games than I ever would against someone like Luck or Rivers. I never understood why people view Rivers as anything but mediocre. Have you ever worried before playing the Chargers? Me either.