This issue is meta issue for text grid related issues. There are two user configuration related to this.
1. Text Grid tab in Page Style dialog, user is able to select among None, Lines, Lines and Chars, and specify grid(base and ruby text) size related settings. Snap to char checkbox is enabled if user uncheck "Use square page mode".
2. Tools / Options / LibreOffice Writer / General / Use square page mode for text grid.
The related odf1.2 attributes are :