His personal ambitions, as far as sports go, are golf-oriented. At least as far as I can tell. He really wants to be an accomplished golfer.
Soccer is more of a thing his parents (coaching) and siblings (playing) dragged him into by the inertia of the family. Same with running -- two of his siblings had cross country or track college scholarships.
I had considered that his sports ambitions might be involved, but does it really make a difference how good a golfer you are as an incoming freshman? (FWIW, he's already big for his age anyway and plays a LOT of golf for his age) I don't know enough about how one becomes a professional golfer to be sure, but I suspect not.
Even if one year of physical development made the difference between getting a college scholarship and not, his parents can afford to send him to college anyway... Are they money-grubbing enough that they would they delay his education for a year to try to increase his chances of a scholarship in a distant, uncertain future? I would not have selected that as the most likely explanation, but I don't know...