Couple of things here:
-you may be conflating biological sex and the concept of gender… as I understand it, trans people accept their sex (external reality) while debating their gender (internal reality) and so they seek to align them
-this internal conflict doesn’t have any direct affect on their ability to judge objective/external reality, their recall, their morals, intelligence, etc.
I personally try to evaluate each person as I meet them and try to be objective as possible. I don’t think categorizing someone with gender dysphoria as untrustworthy by default is helpful in this evaluation.