Requirements for backcourt violation:
1. Team control (and initial player control established at some point if coming from a throw-in)
2. Ball achieves a frontcourt status
3. The team in control is the last to touch the ball before the ball achieves a backcourt status
4. The team in control is the first to touch the ball after it achieves a backcourt status.
Your issue with the play is with the definition of team control and when it ends. Team control ends only if the ball becomes dead, there's a try, or the other team gains control of the ball.