Imagine a team that plays 3 worthy OOC opponents in a season, versus another that plays one. Maybe the former goes 2-1 if it has a CFP worthy team. That isn't going to hurt them much at all if they do well in conference play (which is a given). The latter team has about a 50-50 chance of winning its single game, so in some years they get a black mark and in some years not. I don't think scheduling "up" lessens one's shot at the CFP, if we're talking about CFP worthy teams.
The 3 loss teams THIS year didn't suffer from OOC losses at all, so that couldn't have harmed their CFP chances. As for conference play, it's a crap shoot, some years you're going to miss the better teams like Indiana did and some years you get the hammer. Granted, if Indiana had somehow schedule say ND OOC in the regular season, they would have been out had they lost that one.
A P2 team that goes 11-1 likely will slide into the CFP as an at large, but the road will then end shortly. Maybe they shouldn't, but they will.
Did Indiana have a softer conference slate than others? Sure. Did they contrive to do that? No.