This is an excellent warm-up drill to perform prior to front or overhead squats. Thoracic extension and shoulder flexion are combined movements. It makes sense to focus on promoting both movements and this drill does exactly that!
Everyone may not be suited to jump into this exercise as it can be pretty difficult! So we came up with a nice regression using a resistance band anchored overhead to assist moving the arms overhead. Be sure to try the weighted kettlebell/dumbbell version first, then try the modified version followed up with the weighted version. You'll totally notice a difference. The band is so great because it guides your arms overhead as you focus on your balance, and keeping your torso upright.
The goal of this drill is to maintain and sustain as upright a posture within your capacity. If you practice this drill everyday, it should improve and get easier in time.