I have a nearly 15 yo DD2. Her 'room time' is 9.30 on weekdays, 9.45 on weekends. When she was 13 it was always 9.00. When DD1 was 13, hers was slightly later (9.15)
I have always enforced a time they must be in their own rooms at night. I can't make them go to sleep, but I can make them stay in their room. They can read or text their friends if they like, but they don't come out of the room
So yes, they are organising their own time. Bur in their bedroom after a certain point. DD2 has an ensuite, a bowl full of fruit and other little snacks, all her school books, a lot of reading books, her phone... all in her room. She can choose to do what she likes with them and she can set her own sleeptime. Only rules are...no coming out of your room unless in emergency, and no making a racket loud enough to wake DS up.
It isn't anything to do with 'they must do as they are told, and i am the boss' It is about giving them structure. Children develop best and feel safest when they have structure (mine definitely would go off the wall in behavior terms if they could do what they liked when they liked). This includes younger teens. Far from retarding their development, it helps them develop. Their are other things you can do that will give them the freedom and responsibility they need to develop in other ways e.g. You get given all your holiday money at the start of holiday and you can spend it when you like on what you like. No more money will be forthcoming though!
Certainly, my DD2 (who has complex PTSD) would feel very insecure and unsafe if she could do anything she liked at night. When I go to bed, the burglar alarm for downstairs goes on, the alarm on DD2's bedroom door gets set. If she goes walkabout at night, the alarm will trip and wake me up. She likes that..she tests it about once every 2 months to make sure I still come to check on her if she opens the door