Even with such a preshared rule book you wouldn't get any FTL communication. You could crate a pair of random number generators this way which will always give the same result. Certainly useful for cryptographic purposes but sadly not direct communication.
Agreed; that's what I was trying to say. Perhaps it's disingenuous to frame the problem in this way (that is, talking about rule books and the like), but I was just trying to make it more relatable to normal human experience.
