Pages 699-702 address this in detail: “The land (France) was divided into loose and shifting territories that owed little or no allegiance to any central autho

Pages 699-702 address this in detail: “The land (France) was divided into loose and shifting territories that owed little or no allegiance to any central authority, ruled across large swathes by noblemen who were little more than warlords” and "Flanders, too, had great autonomy from the French monarch and strong ties to Germany and England (Sumption 1990, p. 35). In 1384 Flanders united with Burgundy to create a principality in France that fell in and out of French control for over a century." and "Most critically, (Scotland) was bitterly divided into three warring parts: the English- speaking southeast, the Gaelic-speaking northwest, and the lands that fell between" There's a bunch more detail there along with references to the papers they draw those conclusions from. I'd say they support that part of their argument soundly.