I also love this trope, though I don't know any good keywords to find it. I thought of it as "stoic background suffering", although I like your "adaptation" more. I feel like canon movies/TV series often give the characters some painful background, but then don't really address it, and so I turn to fic for the "adaptation" part.

And thank you for the link to that incredible K/S fic! I just spent most of Saturday reading it in one go :D