Artists often draw their ideas from their own lives, so it is not surprising that they made this movie. And to be honest, what is the difference between Jennifer Boylan's autobiographical book She's Not There and this movie? Different media and different art forms, but they both tell autobiographical aspects of being trans.
I have only seen the trailer, but if Will Ferrell comes across the entire movie defending his trans friend like in the trailer, then this would be a perfect example for others to see how to treat trans folks in their life. So this might not be about being trans, but about being a trusted ally.
Again, I would need to see the entire movie for a final judgement, but I did like the trailer.