(So, notably, in gaming circles I rarely see it used in a place where ‘in the fiction’ wouldn’t work. In narrative and film studies it actually is more specific, and has to do with parts of the fiction as they apply to the overall narrative. Like, does the thing happen on screen or off? Either way it happened in the fiction, but one thing happened in the fiction we saw, the other in the fiction we did not see.)
(I’ll stop being a wank now, I swear.)