Code duplication differs from single source of truth applied to data in the sense that data is data but two pieces of code may functionally be the same (they do the same thing) but they might be semantically different in their usage (they’re advertised to achieve different things), in that case coupling them together with deduplication and forcing them to do the same thing doesn’t really make sense, and may make the codebase more difficult to work on in the future (especially in companies where different teams have responsibilities over different parts).