There is no one glove fits all approach for player development. Some need more hands on, specialised guidance from the best coaching staff you can provide, others just need lots of repetitious experience against the best opponents one can provide them on a consistent basis.
Wilson is only likely to get just a handful of appearances off the bench for us atm at most. Same with on loan at other PL clubs. The Championship is a physical league, and Wilson can learn a lot practising his skills and decision making at that level against predominantly seasoned campaigners rather than in the U23s.
The club obviously consider that to be more useful for his development. If he genuinely starts tearing up that division, he'll earn an extended spot in the first team squad and the chance to compete for srarts. If not, sure, he'll most likely be moved on.
But he's just 21. A bit early to write off, no?