In turn based combat you aren't on a timer. No one can go before or after someone, unless they are the designated person in the order list.
If you sit there and do nothing in FFXIII you'll die, even if you have a full ATB gauge. That's hardly "turn based", since there is no "order" to go in. They call it turn based on the box but in reality it's not. They just haven't devised a new word for what to call it.
Chess is turn based. Checkers is turn based. This is not.