When archeological digs find a body they can determine the gender…from the bones. If only DNA is present, they can determine the gender. Gender is set. Until we can inject enough cells into a body with XX or XY chromosomes in a ratio different than their birth ratio, we can’t change gender.
So what are we talking about? What are we describing when we say “trains gender”? Why do people feel they were born the wrong sex? It isn’t biology. This is a psychological issue.