Well that’s not entirely true. If you have three good starters and three excellent relievers that can be enough to win in the postseason, especially with the days off for travel. That’s not nearly enough, though, over a 162 game grind.
In the regular season, if you have fewer studs and more average to good players, and good depth, you can do pretty well over 162 games but that might come up short against more talented teams in the postseason.
I do think there’s something to the idea of playoff baseball being a little different.