While true they would have uneven games, it essentially doesn't matter. Had the game been played and the Bills lost to Cincinnati, given the scenario Bills beat Patriots and Chiefs lose to Vegas, the Bills would still outrank them.
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.