Hello,
The conversion from HTML to DOCX is done through internal PHP classes without using LibreOffice/OpenOffice.
phpdocx only needs LibreOffice to use the conversion plugin based on LibreOffice to transform DOCX to PDF, DOC to DOCX, DOCX to ODT,...
phpdocx 9 added a new conversion plugin to transform DOCX to PDF using native PHP classes.
Regards.