I had an Endo tell me that a patient came to an appointment with her and announced that she was no longer transgender, and left without explanation. I assumed she meant she had completed her transition, but the Endo said sometimes people change their minds.
The whole purpose of the mental health evaluation is to determine if you are experiencing Gender Dysphoria. To what extent a transition one might pursue, is definitely a personal matter. But I don't understand how someone could be misdiagnosed and the "cause" is some other condition. How is that possible? Was the diagnoser incompetent?
I can understand someone changing their mind for a variety of reasons. Pressure from family or friends that they do not want to alienate. Or maybe, as CosmicJoke stated, maybe it is easier for them to not transition. In either case, the individual decided that any dysphoria was tolerable. Again, that is their personal decision, but does that make the diagnosis wrong?
As Chrissy stated, either way, a mental health evaluation should still be in order to determine the why behind their decision, and then to offer support to help them carry out their wishes.