These girls definitely are under the age limit to compete. The Chinese government has a rule that everyone has to be "essential" to the success of the country. Children are sent away to "sports factories" by their parents in order to learn diving, swimming, gymnastics, tennis and other sports. If not, they are sent to military schools to join the Red People's Army.
At the "sports factories", they live the sport they are "forced" to excel at and nothing else matters until they are released back to their parents, which is only when they "retire" from that sport to become a baby breeding machine after marriage.
Americans, on the other hand, have lives, can freely go to the mall or visit their friends, can say bad things about the government without fear of reprisals, do not get punished if they make mistakes while performing, don't eat dogs, can grow up doing whatever they want to do, visit the gym whenever they want, can leave the gym to go home to their parents, do not get kidnapped and brought to "reprogramming" centers, are more creative in gymnastics and don't need to cheat by having a communist country's government strong arm the judges by intentionally having them delay results while other athletes are awaiting their start time and falsifying birth documents