It’s talking about the additional rows that reside within a full screen Bloc not the page, hence the reason they are not referred to as header and footer or navigation. They are in fact special areas for content that are fixed to the top and bottom of full screen Blocs, normal padded Blocs don’t have them. Add a Bloc and then set its padding to full screen, now switch on the additional content areas, put what you want in them.
by default the hero Blocs are set to full screen with a navigation in the top area and a scroll down button in the bottom. When other blocs have full screen padding applied anything can be placed in these areas.
Hope that helps.