I have my doubts about Yichen actually meeting TW. I very much doubt that TW would have left behind a way for the Tangs to contact him, and it’s also highly unlikely that Yichen went to that Danger Zone – after all, the place only opened when TW wanted it to. It could be argued that TW obviously appreciates the old man’s talent, so he contacted him on his own initiative, but I doubt that if TW, in his sleep, had enough perception of the outside world to sense talent, he wouldn’t also have had the perception to realise that an idiot was killing the dragons.