I agree, I also like ciswomen portraying transwomen. Others have a different opinion however, some feel trans characters should be played by trans people as much as possible.
No no my dear, number one rule for passing: The voice is most important. It can clock a visually passable transwoman just as easily as it can keep an unpassable transwoman in stealth. But yes, they probably didn't want a trans character who could just blend in with the crowd, they wanted one who would stick out from the rest and be forced to face struggles with the people around her for being what she is.