That is an unsubstantiated article.
The couples are not yet confirmed to be responsible. They were first tested positive, but no conclusion has been made if they are the source of other known cases, or they are infected by the other known cases.
Did they break the rule? Their first notification was a "inconclusive suspicion" by the test center when they were already in the queue to board the plane to Xi'an at the end of their trip. They proceeded to board the plane instead of staying. Their test was finally confirmed to be positive after they landed in Xi'an.
Unlike any earlier outcry of rule breaking people, there is no criticism or blame to them anywhere in China this time, news or social media. It is still too early to determine if their "proceeding flight" is breaking rules or not. That has to be left to the authority to judge, not by Bloomberg.