While I think many people would also share the interpretation of the previous posters, the word "audible" means "to hear." It has nothing to do with speaking or speech-to-text. So based on that definiton, the phrase "Audible Text Messaging" means: text messaging you can hear. And that's what SYNC does.
Granted, my first question to someone selling this to me would absolutely be, "So can you respond to text messages in any way?" because that's only logical since text messaging is typically two way communication. I love this feature, just wish more phones supported it.. Oh and speech-to-text wouldn't be a bad feature to add-in one day :)