The reason I brought up Richard Arnold is that, during the early years of TNG, I had a contact from western Canada (which also happens to be where Mr. Arnold is originally from) that met and occasionally corresponded with Mr. Arnold. At the time, Mr. Arnold was Mr. Roddenberry's personal aide. Roddeberry appointed at least two of his employees (namely Susan Sacket, his personal secretary; and Arnold) to positions on the TNG show staff. Sackett's and Arnold's names appear in the credits in TNG's early years. (In fact, Ms. Sackett made a cameo appearance as a non-speaking extra in "The Neutral Zone".) Mr. Arnold's studio job was as the show's "archivist", which meant that whenever any historical "fact" needed to be cleared, the go-to person was Mr. Arnold, who often spoke on Mr. Roddenberry's behalf.
It is important to remember that Mr. Roddenberry was not actively involved in the show's production after the end of TNG's first year. (1987-'88) But Mr. Arnold remained an employee of the studio (and, if I understood my Canadian contact correctly, also Mr. Roddenberry's personal helper) until some time shortly after Mr. Roddenberry passed away in 1991. My Canadian contact wrote copious notes and even shared private correspondence (with me) that he conducted between himself and Mr. Arnold during that time.
This is not an endorsement of Mr. Roddenberry's views, Mr. Arnold's views, or any judgement of what they did or did not do during that time. I am simply relaying what I learned from my Canadian contact who's activities (occasionally visiting L.A.; also meeting Arnold once in western Canada) were verified by a mutual acquaintance who lived near Los Angeles during that time. Out of curiosity, I corresponded via snail-mail and phone on numerous occasions with either or both of these contacts between 1989 and 2000.
Nobody here has to pay any of this any mind, but FWIW, Mr. Arnold (and apparently, Mr. Roddenberry through Mr. Arnold) did have a significant impact during that time-frame in "officially" proclaiming what became known as "Star Trek fact" (canon) which did shape how Franz Joseph Schnaubelt's work was treated to this day.
I simply posted these findings to inform people on what I was told. As far as I could tell, this is a major reason why the Tech Manual and blueprints were "de-canonized".