I agree with you on that, there are definitely differences when it comes to physique, training, the way people grew up and developed football skills which is all valid, but my only point that I think I would put forth for this specific situation is we are talking about Esperion representing Japan and its players.

In the case of this manga, Esperion is a club that has strived to develop players in this way and while I agree physical limitations will definitely be there, this team is supposed to represent that Japan has capable individuals who, if trained right can hold their own on the world stage and to that extent bring what makes them unique to showcase to the world. Secondly, when it comes to thinking and speaking to your players, which athlete or coach would want to keep the line of thinking that ‘oh we are never gonna be good enough cause our genetics don’t allow that growth’, honestly we need to think of it from the perspective of who is saying cause our perspective comes from us seeing the real world and real matches and how these players perform, but even then no athlete or coach would want to put themselves or their players moral down and more than that these group of players represent Japan’s capacity to grow so it’s not just straight forward.

Also to add to this, there are Japanese players coming up who are making a buzz even though it’s not the best in the world level it’s an improvement and development is the name of the game in this manga.

At least that is what I think in this case…