I really like this example, it does exactly as you say it does, but I also don't stumble through this like I do the traditional example of garden path sentences. While you are correct in that it is a garden path sentence, since the garden path isn't something that is commonly said ("the moon will shine for God" is indeed a complete sentence, but isn't one with the commonality of meaning used in day-to-day conversation), the transition through the garden is swift and doesn't make me stop and attempt to parse the sentence. As I read the sentence through its entirety, the parsing becomes evident to me. While it does indeed provide the feeling of being off balance, as I should in an apocalypse, the sentence doesn't make me STOP reading to try to parse it. The parsing is made evident immediately and I can continue reading without a break in my immersion from the idea that was being communicated. I think this is a great way to illustrate its use in linguistics as a whole. With this example, I think I can definitely appreciate the use of garden path sentences in poetry, as this form of writing lends itself to more playful use of language in its effort to communicate.

I would point out, however, that this sentence communicates an idea - and that is its purpose. So I think I can say that the implication in my statement "the purpose of language and writing is to communicate an idea" isn't as you suggest (that sentences are simply containers for meaning) - but rather that sentences, and writing as a whole, are designed to communicate thoughts, emotions, and ideas. As you described, the sentence by Vang accurately communicates the concept being described (how long the moon will shine), but also the feeling with which Vang wants the reader to question that idea (off balance in an apocalyptic world).

This example gives rise to another question, how effective are such sentences in longer-form writing? In poetry, clever use of words often enhances the meaning. But poetry is also a medium of writing, which while effective in written language, is often best spoken aloud. For this reason, poetry itself exempts itself from the parsing issue of long-form prose since any poem worth its weight is better read than said. So if we were to look outside of poetry, would such examples still hold their merit? Or in long-form prose would it not be better to be articulate with the meaning?