So many golfers I work with sway to the back leg in an effort to “transfer” weight in their backswing. That is a popular but faulty thought. Your body should coil in golf against your back leg. In essence you’re winding your upper body against your lower body to build torque and to get loaded properly. If you sway or and allow your weight to shift to the outside back foot, how will you start your legs forward to initiate your downswing?
Next time you’re practicing, plant an alignment stick along your back leg and work on keeping your back leg angle as you turn into your backswing. A proper coil with your back leg maintaining it’s starting position angle is one of the big secrets to better golf.