Exactly. Tie-in writing is a very different field from mainstream science fiction. So what's going on in Trek Lit can't be taken as representative of any larger industry trend.
Like I said before, the first generation of Trek fandom's organizers and fanfic writers were overwhelmingly female. That's the generation that gave us people like Paula Block and Margaret Clark (I think) as well as other prominent fandom figures like Joan Winston, Jacqueline Lichtenberg, etc. The early Pocket novelists were primarily female -- Vonda McIntyre, Sondra Marshak & Myrna Culbreath, Sonni Cooper, A.C. Crispin, Diane Duane, Jean Lorrah, Janet Kagan, Della Van Hise, Margaret Wander Bonnano, Majliss Larson, J.M. Dillard, Barbara Hambly, Diane Carey, Carmen Carter, etc. It's the younger generation of authors, relatively speaking, who are predominantly male. People like myself, Dave Mack, Keith DeCandido, Dayton Ward & Kevin Dilmore, Bill Leisner, etc. are mostly in our late 40s or so and got into Trek writing about a decade to a decade and a half ago. We're folks who grew up reading the work of the first-generation novelists. And I don't really understand why the gender balance has shifted so far to the male side in recent years. But it's certainly not because of any lack of newness in Trek Lit. It is a relatively new development, compared to even a decade ago.