I've been reading this discussion with bemusement; I think for two reasons.
The first is that I don't think we've got enough data. Overall, I think randomness is still driving the selections. But I realize that's not a fair take on the situation and that there's no reason trends can't be discerned, even if it doesn't rise to the level of proof. The selections might well reflect a coalescing around certain themes or genres; the intersection on the Venn diagram of communal preferences!
But deeper than that, I look at my own preferences. I read a lot of nonfiction and I'd say that I don't like either mysteries or fantasy especially. But while nonfiction's been mostly a nonstarter, I've not felt that we've been heavily weighted toward either mystery or fantasy, much less both. Early on in this discussion I said that I'd characterize our choices as mainstream, and I still think that. (That also applies to our two nonfiction choices thus far.)
The labels don't matter, although our individual perceptions do. I know for me, I don't feel as if we need more variety in genre, as my own sense of being overall mainstream is where I think we naturally fall, but I wish we could get more outside the Anglo-American bias in terms of authors and settings that I think we've shown. But at this point, I'm willing to say that also reflects randomness.