My example was "Our administrator and researcher Steven Avery," which is one person. ... The rule of the definite article in equivalent English construction is virtually the same, with virtually the same exceptions.
And in English this might be one person, maybe two.
"Our administrator and researcher Steven Avery works hard to eliminate fluff and puff from the forum."
"Our administrator (Nick Sayers) and researcher Steven Avery are working to help bring forth the Georgios Babiniotis wonderful grammatical understanding of the heavenly witnesses"
Brian, context is king, in this English and, thus, as you point out, also in Greek.
The lack of the article does not make for any rule.
You got fooled because you brought your previous understanding to the analysis.