This doesn’t sound like the kind of rule the NFL would implement because it legislates fake PAT kicks out of the game. Not that anyone ever does it, or would even want to with the extra 15 yards they now have to cover, but to literally make a fake count for fewer points would be very un-NFL-like.
I don’t ElvisL1ves is right about how the 2 pt conversion has ever worked. Here’s a video from 2012 (jump to 50 seconds in) when the kick was still from the 2 yard line, where the Bears faked the kick and ran it in and got 2 points.
The set of rules quoted by Telemark are the current (2018) rules. Scoring a ‘touchdown’ on either a 1-point or a 2-point try is two points, for either the offense or defense.
But recording a ‘safety’ is 1 point, no matter if the play started as an extra point attempt or a two-point attempt. That, of course, would be extremely rare.
A “conversion safety” is so rare it has never happened in the NFL, only in college. So far.
I was certain that I had never seen it. Turns out I was wrong, because I was certainly watching this Fiesta Bowl game when it happened.
Here’s a video.
Oregon had just scored a touchdown. The extra point try was partially blocked and caught by a Kansas State defender at about the line of scrimmage. He tried to run with the ball and retreated into the end zone, where he was met by a tackler. The ball carrier then lateraled the ball but it fell to the ground, where another defender fell on it. 1-point safety!
Even rarer (essentially impossible) is the safety going the other way, where the defending team manages to down the ball in the offensive team’s end zone while the offensive team still has possession. Still worth one point if it ever happens.