page8
The reference is not clear here, because handling of vertical margins is faulty in LibreOffice and OpenOffice, when the first paragraph has a margin. The “text boundaries” consider the margin-top of the first paragraph, but the section not. The violet area is the background of the section.
I would expect, that for pictures anchored to paragraph similar rules are used in sections as for pages, only that not the page height is the start, but the section height.
Section with columns