Making the shift from the linear vertical scroll of word processing software to the spatiality and recto-verso of the codex altered the rhythm and organization of the text.
Spatiality is associated with three dimensions.
No matter how a purely vertical-scrollable text editor or word processor is designed it can't be imagined to have a three-dimensional appeal functionally (The shadow from pages to the background is not a functional design, it is just there to make it look stylish).
In a recto-verso (left page-right page) styled editor, writer, or processor it is inherently 3D. When you turn to the next set of two pages from your on-screen two-pages, you are essentially flipping--an action involving three dimensions.
This traditionally described the transition from papyrus scrolls where one had to roll from end to end verses the ability in a double sided (recto verso) book or concertinaed map to be able to instantly jump forward to any position hence spatial as against linear.
Without knowing the wider context of the text before or after the given sentence, I do not know if it is referring to conversion of screen to the 3D spatial form of double sided print, or if it is comparing old software to new software.
If it is old verses new then in this context of early word processing or browsing software, it initially only allowed you to roll through the pages from end to end. Modern software has bookmarks, hyperlinks, thumbnails and other means to jump through the text, or out to a reference document and back again (if you so wish), that was not present in the earlier days.
The same applies to the transition from tape (linear access) to disk (random spatial access) and databases from simple linear search to modern relational cloud clusters.