Interesting. Nice little segue to the story arc involving Castle's father.
I suspect that Kate has heard more backstory by this time than the Twinkie ever did -- most people have a lot more story to tell by age 42 than they do at age 22. I think that the question in Kate's mind at this point probably is, have I heard the real stories, or did he make up better ones? (FWIW, I think that he did sometimes embellish 4 years ago, but by this point he trusts her enough to give her unvarnished reality -- but in small doses.)
Kate's wounds are obvious. Castle's are much less-so, but there *are* wounds there.