It's true that is how many (not all) measure QBs. It doesn't make it true that it's a good measurement. I think it's a poor one.
I actually think it's a very good way to measure, myself. Today, everything is driven by Offense. Statistics today dwarf the numbers of QBs from the past. I mean, we all understand this, but Championships are a measure of competition at the time each and every QB was playing. Things that are not reflected in the stat sheet are facilitated by Championships, IMO. As example, lets take Troy Aikman and Dan Marino. You would be hard pressed to find a pure passer that was better then Dan Marino. The guy, as a passer, had it all. Enough arm to make any throw, accurate on the deep ball, lightning quick release, he was really fun to watch play. Troy had more arm and he was more accurate in throwing to a spot, with a lot of velocity but other then that, I'd have to say that Marino was more talented the Troy. However, the intangibles were all Troy, IMO, and that doesn't show up anywhere except Championships. Troy wanted to win more IMO. Troy would not settle for a good game, with his performance or his teammates, for that matter. Troy drove the team. He was the guy who made them go that extra mile. Troy was an unbelievably gifted passer, in his own right. Troy could have played in a lot of schemes and thrown for a lot of yards. He could have put up huge stats, had he wanted to. He could have demanded the ball and seriously diminished the role of Emmitt, had he wanted to. Believe me when I say that if Troy would have made any demand in personnel, he would have gotten it. Troy could have killed the running game and demanded a bigger role in the offense. If he had wanted to post the kinds of Stats that other QBs did, he easily could have done that, but then, the team would not have been as successful. Marino did exactly this and that is why he never won a championship.
That is why I do believe that Championships are the best indicator. There are so many parts of the game that are effected by how the QB plays. Things that never show up in the stat lines. How you manage the game effects the Defense as well but that's not ever going to show up. But without that management and that Defense, you don't win championships.
JMO