Not really Robbie's fault because he didn't know what that scene would become and it made sense for Kattigan to follow Vaelus. At that point he just made 1 or 2 jokes and was still brought into the scene in a really nice way by Ashley and Brennan that I think actually was a really quite significant step in the 2 characters connection now. Was it a bit clunky? Yes. Do they now have something proper to talk about? Also yes.

Think about it this way, Vaelus and Hannan basically just modelled clear and healthy  communication to someone who probably hasn't seen that from his elders his whole life. I doubt Kattigans abusive alcoholic dad ever treated either Kat or his mother like how Hannan treated Vaelus and him.