unless someone who didn't speak French had just guessed at the meaning and latched onto the lack of any separate mention for Roddenberry at the bottom.
I believe that was it, yes.
Additionally, in the days of hastily handtyped library catalogue cards, many such mistakes occurred in the cataloguing, too, especially with English-speaking library staff processing foreign-language books. They've focused on the credits below the title, not noticing the name at the top in large print. They were looking for "de..."/"by...". (As a teacher librarian, I can even imagine a library putting a "F FOS" spine label on it.)
I had been informed that Roddenberry's name was completely missing from that page.
But yes, when the secret came out about the ghostwriting of the "Star Wars" novel, people did start looking at TMP with suspicion.