Trans issues have become as much of a dividing line as the EU/anti-semitism were 16-19, perhaps more so as those issues have become less prominent. I wouldn’t be surprised if there were GC corbynites who backed Duffield, or indeed people to the right of her (since Duffield isn’t seen as on the right by the right) for the same reason. Whilst there will be plenty in the 65 who voted to trigger her who also backed Keir.
Am I wrong to assume that it's a generational divide? I find it awfully hard to imagine "gender-critical" activism having appeal to any significant number of Labour activists my age.