Do you mean at only junior level? I know what you mean but this isn't quite true At senior level Other countries have moved to systems where national team coaches interact with and train the players altogether at least periodically for majot events. In fact, Nathaniel Molin became head coach of French men simply because he coaches the Lebruns. Jorgen Persson designed systems of coaches for lots of major tournaments with Sweden until his retirement after the Olympics. Rosakopf has tremendous control in Germany. So because of China, lots of countries have become more centralized as well if they were not already.
you need to see how they travel out.
WTT is all personal, but some times, the national team coach is the one that get free tickets.
so certain players individual coach won't travel with, due to self funding as the only way through.
Some countries are strict where if they use national team money to travel, they must wear national team outfit, and use the national coach.
if they self fund, they would wear they own clothes.
so when the national team coach is there, he or she, cannot sit when 2 of the national players are playing, due to staying neutral.
This isn't a system per say, but rather, how the coaches travel out and remaining neutral
some times, the individual coaches who do travel out will talk and decide to sit or not to sit in.
so this isn't an ITTF or WTT policy, but rather each teams policy and how they need to adhere to.
Japan/Korea all travel as a team, but they are all individual coaches per say and will have no coaches present (even when coaches travel with). So it is really all internal discussions
