package relationships not available for archived objects
Currently, records for obsoleted items are maintained in the solr index so its resourceMap, documents, documentedBy relationships are available, and people can "investigate the past". However, those same relationships are not available for archived items, leading to an incomplete solution for this use case (accessing package relationships of out-of-date content).
Archive is used to limit discoverability, but it also eliminates the ability to navigate the package relationships.
Note: archive is intended to be used when the owner does not want to update the object, but simply remove it. However, nothing prevents the owner from archiving obsoleted content. So, in fact, the ability to navigate the package relationships of out-of-date content cannot be guaranteed, and is subject to the individual data management practices of content owners.