Kṛṣṇa also happens to be grandfather of Mahārāja Parīkṣit, and Mahārāja Yudhiṣṭhira also happens to be grandfather, being the eldest brother of his grandfather.
So Kṛṣṇa is the authority. Therefore Śukadeva Gosvāmī is giving authoritative answer as it was spoken by Kṛṣṇa. This is the way of speaking. One should cite authority. Śukadeva Gosvāmī was not less authority. As I described the other day that there are twelve authorities.
Out of them, Śukadeva Gosvāmī himself is one of the authorities. But still, he is citing the authority of Kṛṣṇa. That is the way of presenting things. That is called Vedic knowledge, that you must giving . . . whatever you say, it must be supported by the authority. Just like a good lawyer, he gives good evidence from other courts' judgment, authority.