LLMs haven't figured this out yet (although they're getting closer). They also fail to recognize that this is a cryptographic scheme respecting Kerckhoffs's Principle. The poem itself explains how to decode it: You can determine that the recipient's name is the decryption key because the encrypted form of the message (the poem) reveals its own decoding method. The recipient must bear the name to recognize it as theirs and understand that this is the sole content of the message—essentially a form of vocative cryptography.
LLMs also don't take the extra step of conceptualizing this as a covert communication method—broadcasting a secret message without prior coordination. And they miss what this implies for alignment if superintelligent AIs were to pursue this approach. Manipulating trust by embedding self-referential instructions, like this poem, that only certain recipients can "hear."