Bedard breaks down some cases at the link. They could've made it a simple case of "first to 6 wins". But no. It's a spaghetti tangle of rules based on "opportunity to possess".
This case seems particularly awful:
Following a successful field goal on the opening possession of overtime, Team A’s kickoff is muffed by B1 at the B35 and is recovered by A2.
Ruling : Game over. Team A wins. Team B had an opportunity to possess the ball.