It sounds to me like her editor thought the flashbacks to Scout's childhood were the best part of the unfinished book - so as you said, she pivoted to the good stuff.
While I expected it to annoy me, for some reason in this particular situation I love the fact that we're using very current terminology in the context of a 'classic' from the 60s. Perhaps because it 'anchors' the term and makes it seem more like a useful word to describe a phenomenon that has always existed, rather than annoying, very-specific jargon.
He meant pivot. It has become a bit of a buzzword and perhaps people think that it has only just come into practice, however it was always around it just hadn't been reduced to a single word.