Totally agree that anyone can have a moment. October baseball is full of unexpected heroes, and those examples are all fair. You don’t need a star to have a big swing.
I think the difference is probability, not possibility. Maximizing team WAR absolutely matters over a season, but in the postseason you’re dealing with much smaller samples and elite pitching. Having more peak offensive talent increases the odds that those big moments come from players you trust to create damage consistently, not just occasionally.
It’s less about “magic” and more about stacking the deck - raising the floor of the lineup, improving sequencing, and not having to rely on multiple role players all peaking at the same time. Adding Bo does increase overall WAR, but it also concentrates more offensive upside where it matters most in October.
Also, think back to Game 3 of the World Series when critical scoring opportunities came up for the Jays in extras, and the at-bats fell to players like IKF, Clement, or Varsho, who were unable to deliver.