Neverrr had any problems telling apart butch lesbians and men. Butch lesbians look more like women than trans women. Maybe if you only had a split second glimpse you'd be confused but face and body shapes are very distinctive.

I read a theory once that women are instinctively much better at differentiating biological sex of strangers out of safety reasons. Anecdotally I've shown some men photos of trans women in women's sports where to me, it's instantly obvious who the man is (even if the women next to him are "buff"), but they have not been able to pick out which one is the man, which just blows my mind. I suspect the transwomen promoting this myth have the same problem -- they genuinely think that having long hair and a dress makes them look more like a woman than a butch lesbian because men aren't very good at differentiating between male and female in the first place.