Whilst you're right that he stands out physically, it doesn't always work in academy players favour if that is the case.
Kids who develop earlier physically can absolutely dominate games at youth level... not necessarily because they are better players, but because no one can match their physicality.
As they go through the ages and start competing against men, suddenly they are nowhere near as impactful in their performances as they can't exert the same physical dominance, and many struggle to adapt to that.
Not suggesting Mustapha will follow that path, and there are plenty who don't, but it's something the club will no doubt be wary of. I think Ozoh falls into the same category, although his physical dominance does seem to be extending into the men's game from the few Championship games I've seen him play this year - bloke is an absolute unit.
I remember watching a young Victor Moses play against my school team as a teenager, and whilst he was clearly a better player than everyone on the pitch, the main difference was how much faster and stronger he was than anyone else. He scored 6.