When merging multiple pdf ua documents, Tags become nested

When merging PDF UA documents the tags seen in Adobe reader are nested. If merging 200 documents then the tags are 200 nested deep. It does not appear to affect that JAWS reader can still read the document  but it may slow down performance when loading to a content repository.

<DOCUMENT>

          <DOCUMENT>

                       <DOCUMENT>

when using Adobe DC to merge multiple documents the tags are flatten

<DOCUMENT>

     <DOCUMENT>

      <DOCUMENT>

      <DOCUMENT>