When leaving the management office, Angor did not really believe that he just got what he needed so easily from Melantha. Also, Melantha set up a condition for him; he must not abstain from any match until he was allowed to surrender.
And Angor did not have any problem agreeing to it.
His exceptional case would not affect the fairness of the matches. However, he did wonder why Melantha agreed to help him when they hardly knew each other.
Angor could not think about any reason and so, in the end, he concluded that Melantha was only a certain individual who was willing to help him out of kindness.
He had forgotten that Sunders gained the records about his matches because the man had some kind of connection with Sky Tower. Melantha, as one of the managers in the tower, should certainly know about Angor's true identity, and it was natural that she would help him when she knew Sunders was his professor.