I imagine this is a practical example of tradeoffs and threat models: mapping syllables-to-syllables is quite a lot of information to leak from the plaintext, b

I imagine this is a practical example of tradeoffs and threat models: mapping syllables-to-syllables is quite a lot of information to leak from the plaintext, but if the cost of that was a less suspicious ciphertext in the age of intercepting physical mail, it would have been worth it. In the age of dragnet surveillance and megaflops it seems incredibly weak, especially with smaller messages.