Currently, any format changes made to any writing object will be applied to ALL writing objects in that section (i.e., cover, preliminaries, body, addenda). This keeps your output looking consistent and professional.
If you need a specific style for a single object, try customizing 'Heading 5' and use that. Typically, most writing projects don't need 5 levels of heading, so this one is a 'spare', and can be used as you require.
Contact the Support Desk if you need further assistance.