Upload a photo and the same person comes back with hair grown well past the shoulders, with realistic volume, a natural parting, individual strands and soft shadows where the hair rests. What must not move is everything else. The face, the skin tone, the expression, the clothes, the pose, the lighting and the background all carry over, because a preview is only useful if the length is the only thing that changed — if the face shifts too, you are looking at a stranger with nice hair and it tells you nothing about whether to grow yours out.