Silmarillion - Valaquenta

[Nogrod]

I'm no Tolkien scholar myself, far from it - I only happen to love his world and the stories, and the stupenduos enormity of the scholarship and imagination that is put into it. So correct me if I'm wrong here, but when Aiwendil says:

A question occurred to me as I re-read the Valaquenta for this discussion: why is it there at all? Most works of fiction do not devote a chapter at the outset to describing the characters. Why did Tolkien feel the need to stop the story and tell us about the Valar before he went on?

Doesn't her first speculation above the question, namely:

One answer is that it lends verisimilitude to the text – if the Ainulindale and the Valaquenta were real texts, written by different (and possibly unknown) authors in the distant past, we would expect them to go over the same territory a little bit.

already answer this?

What I mean is that at least I have had the impression that Tolkien was writing these stories or tales as kind of actual accounts written by different persons in the world he had created. And those writers should have a history of their own and thence a knowledge (fair or bent) of earlier stories which they interwoved into their own writing.

Then it would not be a question about why Tolkien, the Author, decided to devote a chapter at the outset to things He had already told, but of his intention of making stories springing right up from a world he had created - like giving that world an autonomy to tell its own stories? Like if in RL-world histories one (calling her/himself only the compilator of the stories) piled up the stories of, say the Deluge, by first giving the Biblical account of it and then presenting the Qu'ran version of it (okay, a bad analogy, but I hope you see the point)?