They wouldn't have been told anything about the bonding. The oracle once told him that the bond is the most natural, untainted process on this earth, and he didn't want to taint their perception or give them any preconceptions about it as each would be completely unique depending on how each dragon chooses its tamer and what their own bond is like. They probably would have gotten the idea of telepathy for communication from Obsidian Nova when they first met him, but they wouldn't know that their minds would be completely opened to their dragon and vice versa