You are reminding me of something I just read. tell me what you think of it. I am not sure, "Hans-Georg Gadamer, after all, was a major hermeneutical thinker who taught the important hermeneutical truth that an author's intention cannot be allowed to control the meaning of a text."
Before I answer very firmly here I'd prefer to know where you've drawn this quote from.
Be that as it may, the main thing I'd say is that where the "original authorial intention" is concerned, Gadamer disagreed on certain points with Derrida's postemodern insistency that the text essentially loses authorship and becomes the realm and reign of the reader. For Gadamer, and for other later Philosophical Hermeneuticists with whom I'm more familiar, to say that the text goes beyond the author himself or herself is to instead insist that the intertextual situatedness of a text is, and was, always much wider than the mere, selective intention of the author to write. Knowing this, it is up to the reader to be responsible for the sake of interdisciplinary self-education to not simply appropriate the text for him or herself as he/she sees fit.
On an epistemic scale, some of the contrast (and methodological and ideological) conflict between Gadamer and Derrida can be seen by understandking the difference between Critical Realism and Anti-Realism.
So if something is inspired by God is it really necessary for the writer to understand it or intend it?
How do we know if something is inspired by God? I'm not the sort of philosopher who just takes it as a given because someone slaps a Bible in my hands and tells me, "It's the Word of God." I'm going to assume you don't either. There are complex reasons 'why' we each even deign to think the Bible, collectively considered, is inspired---whatever inspiration actually is.
Especially in the same way that we might now thousands of years later?
Again with the OP. If Genesis is post exilic does the intention of the author change the theological message?
It depends on who is writing and asking "how would he [or she] know?," especially the much, much, much further out one goes in time. I mean, I'm not assuming angels just show up out of nowhere to drop huge nuggets of Divine-Info about "THE PAST" into people's brains. At least not at the drop of a hat. So, if the O.T. is Post-Exilic and not contemporary in conceptual alignment with the contexts of the writing, generally speaking, even if not in exact corresponding fashion, then I have a difficult time applying any method by which to make heads or tails coherently out of the nature of what it is I'm reading in the Bible.
So, if the O.T. is all Post-Exilic, that makes it highly suspect to me and I'm less willing to give it the benefit of the doubt as I sift through what other outside historians and archaeologists find in comparative historical inquiry.
And in regard to Biblical critical methods:
Form-critical, redaction-critical, and literary critical methods develop, correct and challenge theological understandings but do not replace them.
Maybe, but from what I've seen across the board in and within academia, whether or not Critical Scholarship "replaces" theological understanding depends upon who you're asking. For some, it does replace it.