Hello,
The behaviour of the enforceSectionPageBreak option is the same for phpdocx 7.5 and phpdocx 8.0. This class (MultiMerge) is the same in both versions of the library (the only change done is to replace .inc by .php extensions).
On https://www.phpdocx.com/news/post/phpdocx-v8-release-notes/214 you can read all new changes added to phpdocx 8.0.
Regards.