Bifolia created using previous as reference

[Jorge_Stolfi]

Wow look, you can see clear instances of the layout being copied and modified. Look at these sequences here. The section on the left splits and gradually separates before snapping back. On the right-side, the left margins all track, which makes sense as this is the last page.

But you observed yourself that the text is split only when and where there is enough room to the right of the plant. And that obviously depends on the plant more than anything else.  Even because the plant is often pushed to the right in order to leave space for the text.  And when there is no split, the right edge of the text is determined by the plant's profile;

All the best, --stolfi