My point is this chart doesn't mean jack squat about how much Exum actually grew, and that its plenty possible for a 19 year old to grow 1".
I'm getting bored so I'll stop after this. The chart illustrates data that helps us to test the reasonableness of the hypothesis. There is no data point on the chart that says "Dante Exum, 2015" so you cannot glean particular data from an average, so on this point you are merely stating the obvious. It is possible for a 19 year old to grow 1" in a year, I made that point earlier. Is is "plenty possible"? I'm not sure how much "plenty" is but gosh, I hope so I'd love to have a more freakishly long/tall PG. The data informs us that this is unlikely, not that it is impossible. Have a great day.