I imagine he is saying that it is theoretically possible for a loose ball to completely leave the field of play at the 2 inch line and touch the pylon after leaving the field of play.
However, the pylon removes any ambiguity in judgement here and simply says that if a loose ball touches a pylon, it went out of bounds behind the goal line.
I hope no one has made the "purist" call because it is not supported by rule.
4-3-3: "If the ball touches a pylon, it is out of bounds behind the goal line."