I think it's because chinese choose to don't join young in international competitions before 15 or 16 years old.
Fan Zhendong began his first competition at 15 years old, and beat a lots of very good players. I think he was a beast before 15, but it's a choice of chinese trainer to keep him in China.
They don't have lots of exprerience when they began against european player and different games, and they have to win all matchs to be in top chinese players. To much pressure on young chinese, no right to make mistake.
Harimoto, in china won't have play before 15 years old, would be less experienced than now.
I think it's a very good choice for him to be in Japan instead of China, because he played lots of international matchs since 10 or 11 years old. He gained lots of experience and have better possibilities to be in national team.
