Naw, I'm just not into anyone with male genitalia at all, even if everything else presents as feminine. To be entirely honest, I'm not sure where "the line" of attraction is for me, since I realize there are a lot of factors at play here, but I imagine it would be decidedly on the feminine side overall.

As for how I know I wouldn't like it, I guess it's like an aversion to something like a food? I just see it and think "no thanks" lol. You're right that I may never truly know, but I'm reasonably confident.