From Middle to forehand corner, There is this coach who teach to step left foot first and then right foot. Most other coaches will teach to shuffle. Even the Pros shuffle from middle to forehand corner.
Step is the basic technique. Additionally, short stature players, e.g. children , won’t have the leg length to shuffle. You won’t go wrong if you learn this step technique. In fact, if you were to coach someone and they can’t pick up the shuffle, you would have to build up from the basics which is this step movement.
Left foot first is very slow footwork because the first left foot step requires a big body turn to step in the correct direction. Any left leg step + right leg lunge movement can be covered by a chasse + right leg lunge. If you need to cover more court with an extra step then it's better to start by moving your right leg towards the corner first followed by the left leg step in front, then finish with a lunge. The first right leg step helps with body rotation so that the next left leg step is more efficient.
Just like what Cheung said, this coach is showing the basic movements to the 6 points of the court. If I were to coach/teach a beginner these would be the footwork steps I would be showing. I would leave shuffle out for a later stage.