You don’t become trans by transitioning. You become trans by your brain being exposed to to much of the wrong sex hormone during early foetal development. It causes the wiring in the brain to largely develope according to the opposite biological sex. By the time gonads are present all the hormones in the world aren’t going to change what is hard wired into the brain. So if someone who is for example genetically and phenotypically male has a female brain, and they choose not to medically transition it doesn’t mean they’re cisgender. It just means they’re sad.