I'm pretty sure that if the Bills win and the Chiefs lose, the AFC championship game is in Buffalo no matter what because they have the head-to-head against the Chiefs (and a better win-loss record) and would hold a better record than the Bengals.
I actually think it makes a ton of sense after parsing it all out. I'm impressed even. It does the least amount of damage possible. I think the only messy bit is if Baltimore beats Cincinnati and they happen to meet again in the playoffs. Having home-field advantage come down to a coin toss won't feel great. I bet the NFL is praying this situation doesn't happen.
This is incorrect. Bengals would also be 8-3 against common opponents with a victory over Baltimore. That would move tie break to strength of victory which goes to Cincinatti.