It sounds like he had a great tournament. It'll be interesting to see what happens to him.
I think CM is a very difficult position for big six clubs to bring youth players into the team. Obviously a player needs technical ability but the combination of physical and tactical requirements is just really high and unusual to find in a young player. And with the way the game works now, you can't let a young CM learn on the job or he will lose you points. Unlike a forward, there aren't many situations where you can bring the player on comfortably for 20 minutes at the end of a match and unlike a fullback you can't put him out there and give him a relatively simple job to focus on. If you're in midfield you have a ton of responsibility. You can obviously always loan the player but finding the right loan is difficult in terms of a team that plays football that will prepare them for being at a club like Chelsea.
The best "real CMs" - ie, players who could comfortably play in a double pivot (I don't count Mount there) - to come through at big six clubs over the last 10 years and really establish themselves have probably been MacTominay and Winks, which sort of says it all. Some of that is a lack of talent but even when clubs have had players with the requisite talent level who could be developed as CMs they've tended to shift them to other positions where its easier to integrate into the first team (Foden, TAA) or just sold them (Lavia, Guendouzi, etc). Its just much much easier and less risky (although obviously more expensive) to buy young midfielders who have proven and established themselves in the first team at other clubs.
I think Chelsea are facing this problem with Casadei, Carney, and Santos but also United with Mejbri, Arsenal with Patino, Liverpool with some of their young midfielders, City faced it with Lavia, etc. Its hard to create pathways for these players.
If I was the agent of a top young midfielder, I would rather my player be at a smaller PL club and only look to move to a big six club once they'd established themselves.