19D is especially rough, if the seatmap starts off as a standard 757 where 19DEF all have excellent legroom. i wouldn't expect that on LAX-JFK.. but, if he's used to 19D on the standard 757, i could see the confusion.... still, suck it up and move on, especially if 19E is your traveling companion!
i remember a guy showing up for the exit row aisle waaaaay in the back of the 727, where it's a pair of seats just in front of the door, crammed right up against the row in front of it. there was an initial reaction of dismay, and then he sat down and that was it. bet he didn't make that mistake a second time....