I would like to make a few points here.
To say he hadn't kicked on is a bit harsh, he is still an under 18 player, barely played U18 last year when he was under 17, as he was pushed up to development squad.
Dapo is two years older in football terms than NYC. Dapo not involved pre-season, contract issue ?
There are a number of reasons youth players are unsettled. At an important stage of their career where and when will they play their next game ? U18 & U23 leagues in England will get up and running, it is not certain Scotland's U18 league will happen. And above that age group Rangers are looking at friendlies at best.
Fairness and money is of course also a factor, it would appear that a EPL academy player is valued significantly more than our own academy players.