You're right! With Cleveland at #5, if you then you concede that two teams will come out of the AFC South at 10-7 (one division winner, one WC) and a third will be 9-8 at best (which is guaranteed because of IND-HOU matchup), that means there is one WC left for BUF/DEN/PIT/CIN.
And as I said long ago, all this talk about tiebreakers will be moot and 10-7 will make it because it does 99% of the time.
The seeding stuff was correct. The only thing that was incorrect was the playoff clinching at the end, because it's actually easier than the tweet suggested. There will be a be a new tweet.