While both techno contras and gender-free dances challenge specific assumptions of "traditional contra dance" (and thus do probably count as syncretism in a broad sense), the two underlying assumptions are qualitatively different. Gender-free contras challenge the heteronormative idea of men only dancing with women and women only dancing with men, and of the roles' definition coming from the gender of the person dancing it. Techno contras, on the other hand, tend to define themselves by changing the music, usually through adding some sort of electronic element (usually involving prerecording at least some of the music).
The main reason that so far I haven't included more coverage of the gender-free contra scene is that I haven't been to a whole lot of those events. (They don't tend to happen as dedicated events in DC that I'm aware of, although role-swapping does happen in the breach, by necessity or volition.) That said, I don't understand why the two sorts of events get lumped together, New York City's gender-free techno contra dances notwithstanding. It seems to me that "they change some aspect of the traditional assumption" is a really, really broad brush and shortchanges the importance of examining each of those assumptions individually and why they're part of the living Tradition.
If someone else can see a more coherent reason, I'm certainly open to discussion and welcome your thoughts.