I’m just looking at Westcott’s classic commentary on the book of Hebrews (3rd edition, 1906), and am pleased to see that before “postmodernism” ever became either celebrated or denigrated, he already rightly saw that our aim is not simply to recapture what was in the mind of the author:
Every day’s study of the apostolic writings confirms me in the belief that we do not commonly attend with sufficient care to their exact meaning. The Greek of the New Testament is not indeed the Greek of the Classical writers, but it is not less precise or less powerful. I should not of course maintain that the fulness of meaning which can be recognised in the phrases of a book like the Epistle to the Hebrews was consciously apprehended by the author, though he seems to have used the resources of literary art with more distinct design than any other of the Apostles; but clearness of spiritual vision brings with it a corresponding precision and force of expression through which the patient interpreter can attain little by little to that which the prophet saw. No one would limit the teaching of a poet’s words to that which was definitely present to his mind. Still less can we suppose that he who is inspired to give a message of GOD to all ages sees himself the completeness of the truth which all life serves to illuminate. (pp. vi-vii)
It seems to me that Westcott still believes in an intentionalist hermeneutic. He’s just saying that the author of Hebrews didn’t catch everything that was intended by “the prophet” — that is, by another intending human, the one in which Westcott is interested. He’s clearly *not* saying that meaning is something separate from authorial intention.
I take “the prophet” to be the author, whose literary encapsulation of his vision was precise, and yet majestic to the extent that it was bigger than the author himself could fully exhaust. So the task of the interpreter is indeed to recapture the vision of the author, but not to feel bound by the need to remain within the confines of what the author exactly had in mind when they dictated.
So you’re right: he’s not saying that meaning is separate from authorial intention, but he is saying that meaning is bigger than authorial comprehension.