It makes perfect sense. The liberal case for transgenders is that gender on the outside does not always match what's on the inside. So your disinterest in t-girls shows you don't really like 'girls' or that you don't truly believe there are girls stuck in men's bodies. You like girls that were born as girls. You have no interest in a girl in a man's body which liberals will die arguing is the case for transgender individuals; their actual gender on the inside does not match their body. And trans-operations can make their bodies better reflect their actual gender
She is a girl right? regardless of what operations she has or has not undergone, that is a girl that was born with male genitalia right? You take away substance to the transgender argument by admitting/believing you really are only interested in the opposite sex that was born with the body of the opposite sex. You devalue the argument that people are not always born with genitalia that reflect their gender by not being interested in girls/guys who were not born with genitalia reflective of what sex they are on the inside