This is spot-on. We never will know what Montana would have done had he gone to three more Super Bowls, because, well, he did NOT go to three more Super Bowls. He *did* have some bad playoff games:
1/6/85 vs Chi: 18-34 (52.9%), 233 yds, 1 td, 2 int
1/4/87 vs NYG: 8-15 (53.3%), 98 yds, 0 td, 2 int
1/9/88 vs Min: 12-26 (46.2%), 109 yds, 0 td, 1 int
1/23/94 vs Buf: 9-23 (39.1%), 125 yds, 0 td, 1 int
So it's not like it's impossible to imagine him having a bad game in a Super Bowl. The more times you get there, the more likely it is you're going to lose eventually. Mariano Rivera is the greatest closer in baseball history, but he's blown a LOT of games. How? Because he's constantly in a position to save the biggest games of the year. Nobody is perfect, and losing and failing is all part of it.
Anybody who holds Brady's 2 SB losses against him compared to a guy like Aikman, for example, who never lost (and they have the same # of SB wins) is crazy. Because Brady has been to two more SBs than Aikman did!!!