First off, don't think I don't see the game you're playing. This is a 'gotcha' question, not honest interest.
But I'll still answer you seriously.

Before transition, society sees women of trans experience as men. Even though they're not.
And many women of trans experience even act like men, try their hardest to behave like men. Even though they're not. Because they're ashamed, and bc society is generally awful to trans women.
Trans women, trans men & nonbinary people don't "become" something else when they transition. They just finally let it show. They finally gather the courage to show themselves to the world.
A person's sex and gender are both stamped on them in utero, before birth. Sexual (gonadal, chromosomal formation) is established during the first testosterone storm, usually at around six weeks of gestation.
Gender (neurological formation) is dictated by the second testosterone storm, in the second trimester.