Ah ha! That's it.
Interesting observations as I run the playoff simulator. Assuming we beat the Steelers, lose to Chiefs, and beat the Browns, we really need the Texans, Broncos, and Bills to each lose one game. If any of those teams goes 3-0 we are likely out. So if the Bengals go 2-1 we are likely looking at needing the Dolphins to beat the Bills in the last game week 18.
However, if the Bengals should go 3-0 we would need, in retrospect the Texans to beat the Browns to pretty much lock up the 5 seed. If the Browns win next week against the Texans, and should the Bengals go 3-0 they would very likely lock up a 6 seed regardless of what the Broncos and Bills do.
If the Bengals lose to the Steelers, they justifiably are pretty much done.