The hip only has a few parts, and the same sequence of development of those parts occurs in the same order in a baby multiple times. The drills show you train the same progression.
When doing squats with two feet on the ground, you are simply insuring that you have enough power in the hips relative to your body-weight. If you cannot perform a squat easily, it would be impossible to control your body anymore than you could fiddle with the gears on a car that doesn’t even have enough power to get the car moving in first gear. Just think of this component as the glutes.
The second stage (show link) for the hips involves having enough power to move temporarily bear weight on one leg, then push while turning back to the midline. This requires simultaneous action of the glutes, as well as the abductors and external rotators. This is clearly a balance reaction.
What follows is learning to use these three parts (glutes, abductors, and external rotators) in a sequence. They go from being one movement in the brain during balance reactions to being separated one by one. During the one foot jump, the glutes and abductors are active as the external rotators are letting go. During the ballet stretch, the glutes are still active as the abductors let go.
As the external rotators learn to let go as is trained in the one foot jump, the internal rotators (TFL) are actually turned on. This is what what happens in the front hip in the backhand tennis, which is the same as the golf swing.
So here is the sequence of drills to develop good coordination if the hips, which is necessary for every activity. Squats, frisbee, one foot jump (hip strengthening/stretching drill), Ballet stretch, backhand tennis.