He says he won’t discuss the events of the last two months, but he’s clearly picked up some terminology and self-narrative in therapy. Not insight, of course, because he’s a retard, but a narrative that he’s parroting from the doctors he was seeing.
The “generational trauma” bit is the most obvious thing he’s learned, but in addition, the exercise of comparing and contrasting himself and his mother is likely a repetition of something he did in therapy.
I’m also inclined to believe what he says about Barb’s response to learning that he saw a prostitute - he’s bringing it up in the context of a discussion of emotional incest, which, crucially, he never understood before, nor did he think it was wrong or unusual. In the past, he has seemed at most a bit annoyed by Barb’s possessiveness, but didn’t show any awareness that it was abusive or morally wrong by social standards. His thoughts here show a genuine change in his beliefs and perspective.
The pessimistic response is that he’s just trying to absolve himself of responsibility, and that’s partially true in all likelihood. But there’s an undercurrent here that shows that Chris’ time in the mental hospital has changed his perspective on some of his past experiences, and he is not happy about what he has learned.