you don't go to the playoff no matter who you played (with the possible exception of the SEC). Since losing to a bad team is a lot less likely than losing to a good team, the logic here doesn't make sense to me. If they'd made the argument that winning the CCG against a good team (rather than a bad one) might lock in a playoff spot, I'd agree.
As for the G5. I think a loss in the CCG, regardless of the opponent, would likely kick the entire conference out of the NY6 and leave an opening for some other conference. If Boise had played, and lost, to Colorado State, odds are that Marshall would have gone to the NY6 bowl instead.