The Chinese FA Cup semi-finals are set to be played in a round-robin format, which means that each team will play against every other team twice. The first leg of the match will take place on September 12th, while the second leg will take place on September 19th.

This format was chosen because it allows for more competitive matches between teams, as each team has the opportunity to face all other teams. It also ensures that there is no repetition of games, as each team only plays once.

The round-robin format also makes it easier to predict the outcome of the tournament, as there is less uncertainty around who will win each game. This can help fans and analysts to make more informed predictions about who will ultimately come out on top.

Overall, the round-robin format is a good choice for the Chinese FA Cup semi-finals, as it provides a level playing field for all teams and helps to ensure that the competition remains exciting and unpredictable throughout the tournament.