The Deadly Sin, 'Gluttony', had taken the risk to seal itself in order to enter the trial without triggering the self-destruct mechanism. It was certain that its goal was indeed Shi Xiaobai.
Kali had previously speculated that Gluttony was likely using its instinct to find the awakener of the Original Sin of Calamity or other Deadly Sins which resulted in it being so careful. And clearly, Shi Xiaobai was not one of the Deadly Sins because he did not have the characteristics of the seven Deadly Sins like Pride and Gluttony.
Therefore, the greatest possibility was—Shi Xiaobai was the awakener to the Original Sin of Calamity.
Before the Original Sin of Calamity awakened, the awakener would be no different from any other human. It would have its memories as the Original Sin of Calamity restored after it awakened; therefore, the possibility of Shi Xiaobai being the Original Sin of Calamity was extremely high.