Yes, when I was younger I also believed TWAW. I accepted it when I was told a "woman's" brain could somehow grow in a man's body because of hormone washes in the womb, and that such people were really women in some essential way and lived very sadly until they had sex changes and were recognised as women, and that males and females have similar physical strength but females are socialised not to push themselves as hard, and that trans women were very vulnerable and at risk of violent attack if anyone clocked them as trans so they needed to be in women's spaces for their own safety and only a bigot who was trapped in rigid gender roles would object to that.
And then I thought, "hang on, I don't even believe that men and women have different brains so how does that even work?"
And then Monroe Bergdorf complained about women protesting Trump's "grab them by the pussy" comment in pussy hats because it excludes trans women and I thought "hang on, he still said it, and he said it about us precisely because we have pussies, but you are taking away our language to object to it, so you really don't see yourself as one of us because if you did you'd understand that even if it's not important to you it's important to us and you'd support us"
And then I found out that most trans women keep their penises, and that teenage boys routinely beat women's world records in sport, and just how stark the difference in sexual offending is between male and female people, and that the UK murder rate for trans people is well under 1 a year when for female people it's more than 2 a week...
So like many things I believed when I was young, I stopped believing it because the longer I live, the more I learn and sometimes I realise things I deeply believed were wrong or at best over simple.
Although to be clear, I still support trans people to be the gender they want to be.
I just no longer believe that inner gender is somehow interchangeable with sex, nor that trans women can slip without issue into all the structures that were built for female bodied people and that have no impact on the female people they were built for.