I saw that at the start of 3OT, each team had a choice to go on defense first or 2nd. Each time when given the choice, the team chose to go on defense first. I thought this was interesting because I would have thought you would want to let your team rest for another play and make the other team's play defense first, giving them less rest.
Since by the 3OT, teams just go for alternating 2 pt conversions, there is no mystery involved. Either you score 2 pts or no pts. You don't have to wait to see what the other team does first. Might as well let your defense rest.