[Legolas]

If you're looking to understand the author's intention, the purpose of the event in the book, it certainly can matter. It was originally posed "give me a good reason why Gandalf had to pop up out of the abyss." Whether you care personally what Tolkien thought is not the question. Looking to the author for reasoning is a good way to start. No one is supposing such statements will outweigh the evidence of the story. They supplement the evidence in the story; they bring it into perspective.

As noted in the post that provided the quote, Tolkien does not appear to be "embarassed by the credibility of having a character return from the dead," but rather by the way he handled it within the story.