How accurate is the statement of al-Hafiz Ibn Hajar (may Allah have mercy on him) at the end of Lisan al-Mizan, after he mentioned that he had included the weak narrators whom al-Dhahabi did not mention in al-Mizan?

The questioner : Al-Hafiz Ibn Hajar (may Allah have mercy on him), at the end of Lisan al-Mizan, after mentioning that he had included the weak narrators whom al-Dhahabi did not mention in al-Mizan, said: "And whoever is not mentioned in this book is either a trustworthy narrator or a hidden one". So how accurate is this, meaning...

The Shaykh : It is not certain, and this is the opposite of the other proverb, "The first left nothing for the second"; rather, it is "How much did the first leave for the second?". Therefore, if one adds to al-Hafiz's work some narrators, even from those mentioned in the well-known sources from which al-Hafiz took the material for his book, that is certain in general, but not in detail.
And the rule you referred to, that he is either a trustworthy narrator or a hidden one, where is it derived from? He did not state this explicitly, as he did, for example, regarding the hadiths about which he is silent in Fath al-Bari. Rather, this is also a conjecture by some of the reviewers of his book and those who benefit from it. So I do not think this statement is entirely sound.