Some authorities proposed extra criteria for Successor status, such as extended association, sound direct audition, or discriminating maturity. The preferred definition discussed here does not make those additional conditions indispensable for identifying the generation; a qualifying encounter with a Companion is its core.
Yet calling someone a Successor does not establish that every report attributed by that person to a Companion was actually heard from that Companion. A Successor may have met a Companion but received a particular account through an intermediary.
Two separate investigations: proving that two persons met concerns their historical classification; proving direct hearing for a particular report concerns the route of that report.