You would know, wouldn't you? You watched it all unfold the first time they did it. They've only gotten stronger.

[ Well, in some ways. In others, they've all but fallen apart and Castiel's had a front row seat to it, but Chuck doesn't need to know that just like he doesn't need to know about Castiel's mistakes. It's nice to have one person who still thinks of him the way he was, even if it's a lie. ]