As I said, good luck to him. I'm coming more from risk management perspective and he is definitely not taking the most risk-averse option but as you said, he is backing his own talent. Wouldn't be the first to succeed elsewhere nor the first to fail.
If his aim is to be a pro footballer then he actually is. Because these years now he needs to play regularly and his past 18 months at United have been mismanaged in the fact he neither played or was sent on loan (even when he insisted in the loans since Jan 2019)
So it would be a mistake in terms of the risk to continue at United in that sense.
Similar thing happened with Pereira who stagnated quite a lot as a result. I'm not saying United are not good at developing talent, we are one of the best, but even so some players will stagnate because other are fast-tracked ahead etc
Staying at United for him at present time doesn't make sense, especially when he only got around 45 min last pre season.
If you're talking about risk management the biggest risk at his age is lack of competitive game time.
Anyway let's not derail this thread, happy to discuss further in another thread if you really want to