That can't be right. Far be it from me to argue with the pros, but the dead ball rules don't change in overtime, so a play isn't over until the whistle is blown in OT just like in regulation. A whistle isn't going to be blown unless a player is down, the ball goes out of bounds or a player scores.
As I mentioned above, an intercepting team that doesn't immediately get down on the ground could conceivable fumble the ball back and a ref isn't going to blow the whistle until that player is down. If the play ends in the end zone with a player in possession of the ball, points will be scored.
From NFL.com, these are the ONLY
rules that pertain to overtime. Nothing is said about scoring plays differently, thus one has to assume a pick 6 counts as such in OT just as in regulation.
Digest of Rules Main
The sudden death system of determining the winner shall prevail when score is tied at the end of the regulation playing time of all NFL games. The team scoring first during overtime play shall be the winner and the game automatically ends upon any score (by safety, field goal, or touchdown) or when a score is awarded by Referee for a palpably unfair act.
At the end of regulation time the Referee will immediately toss coin at center of field in accordance with rules pertaining to the usual pregame toss. The captain of the visiting team will call the toss prior to the coin being flipped.
Following a three-minute intermission after the end of the regulation game, play will be continued in 15-minute periods or until there is a score*. There is a two-minute intermission between subsequent periods. The teams change goals at the start of each period. Each team has three time outs per half and all general timing provisions apply as during a regular game. Disqualified players are not allowed to return.
*Exception: In preseason and regular season games there shall be a maximum of 15 minutes of sudden death with two time outs instead of three. General provisions that apply for the fourth quarter will prevail. Try not attempted if touchdown scored. If there is no score in the 15 minutes, the game shall end in a tie.
"You stay bought into it when you see your opponent sucking air and physically failing, and you're still fit and ready, and you know you own his ass."
-Former Bama LB Cory Reamer on Coach Cochran's training program