And I for one love reading that kind of thing, in any universe. I've been known to laugh out loud and mutter "Oh, you clever s.o.b.!" when I come across something like that in anyone's work.
My other DC Fontana anecdote:
Her novel "Vulcan's Glory" (Feb 89) was in final revisions at about the same time as the "Spock will have a brother in ST V" rumours, and people in my club were anxious about whether she'd have had time to be able to address the issue in the novel, since the film was due in June of the same year. In media interviews at the time of Director Shatner's announcements for the movie, both Roddenberry and Fontana doubted that Spock ever had siblings (and in memos during the show in the 60s, Fontana would suggest that not having siblings made Spock more unique).
I was kinda, sorta, almost expecting a line in the book about Spock having no brothers, but one that left wiggle room for fanon interpretations that wouldn't be undermined by the still-to-come canonical movie, but DC actually went one further and had Amanda say to Spock, "You are the only child of Sarek."
DC wasn't breaking canon, since that movie wasn't out yet, but it was a sneaky little line that even ruled out half-brothers, and could have been so easily swept away by an editor's red pencil. Or had she written that line long before the news even broke?
When I asked her about it, she gave me a sly grin and said, "I'm thrilled that you noticed."