An interesting test in epubcheck invalidates a circular set of refined metadata expressions:

<meta property="belongs-to-collection" id="c01" refines="#c02">col1</meta>
<meta property="belongs-to-collection" id="c02" refines="#c03">col2</meta>
<meta property="belongs-to-collection" id="c03" refines="#c01">col3</meta>

There isn't anything in the specification that makes this illegal, but it does look like a restriction that should be codified similar to how fallback chains must not create loops.