I think they were speaking from a purely real life production and not considering in story ramifications.
IOW, they had a white actor kiss a black actor on tv. Other information they have treated as superfluous, like the actual plot or circumstances or even the characters themselves.
And, whether Elaan of Troyius was on before or after, it doesn't matter. I hate to be so blunt, but it wouldn't count as "interacial" unless it involves a black person, as per attitudes in US, especially at that time. They had seperate facilities for whites and blacks, although they sometimes used the word coloreds. Asians really weren't on the national radar, although there were certainly local incidents of bigotry. Again, I apologize for my comments, I don't post to offend.