It is still very early days for the likes of Chong, Gomes etc. Wan-Bissaka made his PL debut aged 20 years 2 months, McTominay 20 years 4 months, Dan James made his Championship debut aged 20 years 9 months, Lingard's PL debut 21 years 8 months (played Championship a lot earlier), Bailly's La Liga debut came aged 20 years 5 months, Maguire's PL debut 21 years 9 months (played a lot at a lower level prior to that), Lindelof made his sub debut in Liga NOS when he was 19 years 9 months but his full debut in that competition didn't come until he was 21 years 6 months.
It is clear that United under Solskjaer would like to develop our own talent but that will require patience, both from the coaching staff and the players concerned. I struggle to see how anyone can assess how Chong will perform as a mature adult, until he acquires the physical strength to compete in the PL. And then there's the whole mental side of playing for United, can he cope with the pressure ? Will he be a player that improves aspects of his game year after year ?
I like Chong and hope he stays another 3 or 4 years, so we can discover if he will turn out to be good enough or not.
As for the current stories about him leaving, I suspect that is simply his agent examining the options available to him.