The next step in John's lesson is to get his right hip out of the way on his backswing.
Mike makes John drop his right foot back in his stance and wants John to push his right hip back on the backswing. This allows John to have more swing with the right foot back while pushing the right hip back. Having more room gives you more speed for your arms to come down into the ball.
You will likely come over the top with your swing if you don't push your hips back.
Again, pushing your hip back creates more space, allowing your arms to come down and your hands to lever the club.
Mike reinforces to John to work on his new grip and get his right hip out of the way.