There are several other references to God in the quotes at that link. "Mostly didn't [believe in God]" - So you're admitting that at some points in his life he did. And how are you measuring "mostly"? Expressions of doubt don't count; expressing doubt is a core part of the traditional Christian religious experience. Tolkien's expressions of doubt are no different from expressions of doubt from countless Christian saints throughout the ages. I challenge you to find a single quote in which he says he is agnostic or is sure he doesn't believe. You can't. You're confusing expressions of doubt with agnostic attitudes. And if some can be characterized as agnostic in their youth but as they aged expressed more and more certainty as they aged, like Tolkien, how much of an agnostic were they ever really? Conversely, if some expresses more and more certain atheism as they age, how much of an agnostic were they?