Updating prose to be more generic around reflow and resizing of the m…

…ain page content

website/docs/components/side-nav/partials/guidelines/guidelines.md

@@ -142,7 +142,7 @@ On smaller viewports, the SideNav will be rendered in its collapsed state **by d
 
 ### Collapsed reflow
 
-The collapse functionality of the SideNav gives control to the end-user to unlock more horizontal space in the main page. Thus, the main page content should reflow to occupy this space if the SideNav is in its collapsed state.
+The collapse functionality of the SideNav gives control to the end-user to unlock more horizontal space in the main page. Thus, the main page content should reflow or reposition to occupy this space if the SideNav is in its collapsed state. If the main page content has a predetermined maximum width that is reached when the SideNav collapses, the content should transition smoothly to the new center of the main page area.
 
 This is handled out of the box by the [AppFrame](/components/app-frame) component, but may need to be accounted for in custom implementations of the application/page layout.