While I agree with that your scenario would keep a 1-loss Bama team out of the play-off, I don't think that's the only scenario...

If Ole Miss wins out and is SEC champion, there's a good chance Bama is left out, even with just the one loss. There's a decent chance that the Big 10 champ is undefeated (right now I'm guessing it'll be OSU)...and, if Clemson beats FSU at home, they'll more than likely be the undefeated ACC champs. Both of those get in...so Bama's hopes would fall on either the PAC-12 or Big 12...

In the PAC-12, if Stanford runs the table, they'll get in before a 1-loss non-SEC champ Bama team...and if TCU, Baylor, or Oklahoma win the Big 12 outright that could be a problem. If TCU or Baylor finish undefeated, they're in...if TCU or Oklahoma finish as the outright Big 12 champion with 1 loss, they might get in...

And then there's the, albeit unlikely, Memphis issue. If Memphis runs the table, and Ole Miss is the SEC champion...then you have an undefeated non-Power 5 champ that not only has a victory against the SEC champion on their resume, but also a victory over the team that beat Bama...

And then again, if a couple of the other Power 5 champs have 2 losses, if Ole Miss wins the SEC how much value would they award the conference championship? Bama would have only 1 loss, but would Ole Miss's head-to-head win and conference championship outweigh their 2 losses in comparison with Bama in the committee's eyes? Who knows...

I think Bama's only shot is to win out and Ole Miss lose a game...could be wrong, but don't think it likely they get in otherwise unless total chaos breaks out in the other conferences...