they know they have 2 downs to get 6 yards so they deliberately go with the play that they know will get them 4-5 yards knowing they just need to 1-2 yards on fourth down and they are happy with that outcome on 3rd down. So, the problem, to a tangential point you were making, is that conversion down percentage has to be able to know the intent or definition of success for a 3rd down play—which metrics and stats don’t ever give you the ‘intent’—in order to pull any meaningful insights from it.