The quote is on pge. 43 of the book Machine Quilting in Sections, by Marti Michell, 2004. It is the Case Study: Cabin by the Lake.
She is using the whole back and batting, but centering the middle on it...quilting...then adding the borders that will be mitered. On the Issues and Answers concerning this quitl, her comment is under Answers, note #4.