They way I understand it. Is that in the past they were concerned about people moving on for greener pastures. And you would get a tbnt if you seemed to be looking to move on.
Now that the training contract is in place. And people are actually having to sign it. If you're honest in the interview about your career aspirations. And also happy and willing to sign a training contract. Along with a positive attitude and If you seem optimistic about the future of Frontier as a career airline. You will get the nod.
Lying in the interview is easy to spot and will get you a tbnt as well.