Hollywood/mainstream scripts very rarely survive the gauntlet of director, producers, funders, product placement "partners", and studio executives entirely unchanged. All it takes is one person in the chain saying "this doesn't seem relatable to the American public" to force in stereotypes. The bigger problem is most of those aforementioned individuals are from a rather homogenous group so their "horizons" aren't exactly very broad and they are the ones who control the purse strings.

An indie film about transgender people is far more likely to be representative of reality regardless of who writes the script because those films often self select for funding that doesn't come with the same kind of strings attached.