Surely implicit in the statement is "all 2-point conversions in the 4th quarter by the same team" since we are comparing 3 possible 2-point conversions in the 4th quarter by the same team. (2pt conversion when down by 8, 2pt conversion when down by 2, 2pt conversion when down by 1).
Pass plays are less likely to convert than run plays. The conversion rates aren't even equal between teams.
https://www.teamrankings.com/nfl/stat/two-point-conversion-p...