Not necessarily. Every school is required to publish a "Cost of Attendance" that breaks down the costs of expenses such as tuition and room and board. Some schools will publish just one set of room and board costs that cover all possible student living situations (on campus, off campus, at home, etc.), and some schools will publish different room and board costs for different living situations. For the schools that publish different room and board costs, I think it's safe to say that the published costs for living at home are generally less that the costs for living on campus or living off campus (but not at home). These published room and board costs are the maximum that can be taken from a 529 account as a qualified room and board expense, unless the student is living in housing owned or operated by the school and the actual room and board amount charged by the school exceeds the published cost.
The bottom line: find out what your child's school has published for room and board costs, and let those numbers guide you.