But still, doesn't matter whether it is adult or children, Horatius was still the first tie-in Trek novel.
If the person writing the article was thinking in terms of novels for adult fans, "Mission to Horatius" wouldn't have come into his radar.
I realised, after about six months of buying second hand Bantam, Corgi and Ballantine/Del Rey ST novels in 1980, that my younger brother's old copy of "Mission to Horatius" was in our childhood toybox. I retrieved it, but it's not in the same bookcase as my novels. It's on a shelf beside "Trillions of Trilligs" and "A Giant in the Universe".