You're right that the two cases pretty much exclusively overlap, but there's a few edge cases where they don't.

Scenario 1: BYU wins the CCG... but still doesn't make the playoff.

This basically means that BYU loses to Arizona St, loses to Houston and then somehow has every other game go right to still make the CCG, and wins that. But at the same time, Army goes undefeated (including a win over Notre Dame) and Boise St only has a loss to #1 Oregon. So the top 5 conference champs are B1G, SEC, ACC...and then undefeated Army and 1-loss Boise over a 3 loss BYU.

Scenario 2: BYU loses the CCG....but makes the playoff.

BYU defeats Arizona St, stays on one loss for a huge conference championship game with Colorado. It's a close game and BYU looks good, but ultimately Colorado prevails. BYU is seen as a bubble team and it's tight, but BYU ultimately sneaks in as the #12 team, playing Ohio St in the first round.

Obviously neither of those are good or as preferred as winning out AND getting the CCG victory, but scenario 2 is miles ahead of Scenario 1.