^Right. It's not like Arnold immediately stepped into a position of power the day he met Roddenberry. From what I can determine, Arnold came to Roddenberry's attention in the mid-1970s as a Paramount tour guide whose exhaustive Trek-trivia knowledge impressed Roddenberry and led him to call on Arnold for various Trek-related duties. This eventually led to him being dubbed "Star Trek Archivist" sometime between TVH and the debut of TNG -- at which point he'd been working for Roddenberry for roughly a decade -- and part of that job involved assisting Roddenberry in his oversight of the tie-ins. I'd assume he was initially called on for his continuity knowledge, but ended up getting more and more of the responsibility for the tie-ins delegated to him as Roddenberry's health failed.