Not saying you are wrong, but a few things to note / discuss:
The study indicates that CYP17 is a "candidate gene"? It isn't fully proven...
The study indicates the CYP17 gene is valid for FtM but not MtF transitions... which means at best it can only explain half the population of trans right now
The study I linked was done with under 2000 people in 2007, and a later study in 2015 was done with under 700 people. When you compare that to the estimated 30-70 million transgender potential people, the study is lacking in my statistical opinion...
Further, have you considered that maybe trans-racialism simply is too new and hasn't been studied enough?