I agree with Roger,

What is duplicate content?

Duplicate content is content that appears on the Internet in more than one place. ... When there are multiple pieces of, as Google calls it, "appreciably similar" content in more than one location on the Internet, it can be difficult for search engines to decide which version is more relevant to a given search query.
Xara only creates a single file (index.htm) to serve all variants, not several files with duplicate content.