I have a close relative who came out as trans recently. He had long been "gender fluid" and that may actually be what he still is--he has no plans for surgery, just hormones. But I agree completely that he is still the same person as before, and went through an adolescence (as a girl) with the usual bumps and splats.

He is close to 6 feet tall, but that is heredity, not anything that transitioning has done. Before, as a she, he was the same height and bulk and probably (had s/he been interested in sports) have had the advantages that everyone now is shrieking have to do with being trans. In fact, trans kids who become aware early, and have parents willing to allow puberty blockers, don't develop the sex hormones that give them their main "birth sex" characteristics later in life.