I totally get it : " … people have the right to move schools if their heart so desires and that shouldn’t be a big deal." Yes, absolutely, but it’s extremely difficult given the prior three rejections from those schools - which was your question. I didn’t know he was an elite athlete until this morning, but even with that piece in place ( the line forms to the left with elite student/ athletes ) , I still think it’s a tough climb- for anyone .
HT to your nephew who pulled it off and got to where he needed to be . I have three rowers who were recruited ED. Two went to Ivy while the other one chose a LAC/ team who was on a trajectory to beat them. A heart wants what a heart wants… or something. 
It’s all good.
Now that I know the athletic piece… here is a great thread- just in case anyone is interested: