Prophecy: A Cipher for the Readers

That said, now that I’ve realized his three-fold revelation strategy, I see it in play almost every time. The first, subtle hint for the really astute readers, followed later by the more blatant hint for the less attentive, followed by just spelling it out for everyone else. It’s a brilliant strategy, and highly effective.
^{— Anne Groell, GRRM’s editor}

I believe a careful exploration of Martin’s use of prophecies in A Song of Ice and Fire can allow us to make an insightful observation:

Prophecies are a device used by Martin to communicate with his audience – NOT with characters in the books.

As a cryptic form of direct address, the utility of prophecies is often not hinged on the real-world possibilities (meaning as a prophecy might make sense to a character).

Continuing, the value of prophecy is most often derived from things perceptible only to readers (e.g., such as the prose used by the author).