It may be doubtful the 12-team CFP will last long enough for this, but my position is that we'll have to wait something like 10 years to REALLY get a handle on the answer to this question, maybe longer.
There are anomalies in statistics and sometimes the outliers come in clusters. If the G5's win their first two CFP first round games that MIGHT be indicative that they are as strong as some here are asserting and they'll keep that up and go at least 5-5 in first round games over 10 years or those two MIGHT just be the two outliers and after 10 years they'll be 2-8.
Conversely, if the G5's get smoked in their first two CFP games, that MIGHT be indicative that they are as weak as @OrangeAfroMan and I are asserting and they'll keep that up and be lucky to go 1-9 in first round games over 10 years or those two MIGHT just be 40% of the losses that they'll sustain in 10 years and they'll end up 5-5 in the first 10 years of first round games.
Ie, I'm saying that I will neither claim to have been proven right nor admit to having been proven wrong after the first two years of 12-team CFP's.
Medina. My friend. You're one of the people that forces me to think through things in this place, and this post led me down an interesting rabbit hole that I'd not gamed out with the playoff.
SO, my initial thought was, even if they went 2-8, that's maybe what we expect? Like, we'd assume they'd go worse than 5-5, maybe 3-7? Maybe worse? So I figured I'd sketch out the matchups and set lines using end of season SP+ (we can debate if using end of regular season would be better, but in theory, more games means a bigger picture).
And the takeaway was interesting.
See, the standard for 5 seed sort of shifts around. Some years you park an uninspiring UGA team there. Some it's that Iowa team that no one thought was THAT good but was like a yard from the playoff. Sometimes it's Bama.
What's more, we don't really rank teams by how good they might be. We rank them by losses. So some years you might catch a hellacious 9-3 team at No. 12. (SP+ can have some quirks where power rating and record don't align, so I respect it's weird.)
So here's the year-by-year lines for that theoretical game (Not doing 2020 because it was dumb and weird). Using final year SP because it's just much easier to find.
2019 - UGA by 9 vs Auburn (woulda been 11 vs UCF)
2018 - ND by 4 vs PSU (6.5 vs UCF, granted, ND was 13th in SP+)
2017 - Alabama by 22 vs UCF (Bama was Bama and SP didn't like UCF)
2016 - Ohio State by 9 vs OK State (OSU was 10th in SP, OK 14th, but a 6-point difference)
2015 - Iowa as a 13-point dog vs Ole Miss (SP did not like Iowa that year, really liked Ole Miss)
2014 - Baylor by 14.5 vs Ga. Tech
The most intersting part is those 5s, all quirky in their way.
2019 UGA - That team where the offense cratered with Fromm. No one really liked the team, but they were parked at that spot because of a dearth of interesting 2-loss teams and SEC. Oregon probably should've been ahead of them, but it didn't count for much.
2018 ND - Undefeated, uninspiring, sorry good UGA team
2017 Bama - we all thought might be the best, and ended up there
2016 - Of all four OSU team that started Barrett, probably the worst and hardest to watch
2015 Iowa - They were ... fine
2014 - Baylor. All things considered, this is where you'd put them.
Basically, I wonder if they rankings of 5-12 get shaken up because you have more stakes in every seed.