I understand your point but its difficult to judge without knowing all the information and purpose about the drills at hand. That drill is AS-C Basic Drill #9. It works the first step in getting to the volley. I'm not sure if they were using a varient of it because they were going a lot faster but the way we did it was you push off and cut the angle on the volley, then use your front left leg on the forehand side to push back to the T, then repeat on the backhand. Push off and and move in on an angle and then push back with your right leg and move back to the T. Its a drill that isolates a certain movement done on the tennis court and make it better but also working your legs that much harder by having to push back. There are many different levels you can do on court of course in your training as a coach as you know. Feeding to a specific spot and working on technique in a more controlled manner, such as this drill, to moving the player around more but still standing in one spot feeding. Then you can do like in the RPT video and move as you feed according to where the player hits the ball or have set targets. Then theres the more interactive feeding where you feed the next ball according to how the player hit the previous, to doing live ball drills with the player or having 2 players do live ball drills against each other. Like Luis says in the video, each step up the coach loses a bit of control over the situation at hand but the player gains (if done correctly) a more match specific experience. Its the same in the drill from the AS-C video where they had the kids start off at the T, move back, hit a forehand and then come in and hit a volley and then do the same off the backhand side (Basic Drill #7). Of course you would never move back like that if you were playing a match, but thats not the point of the drill. Its not a match specific drill. It works 2 things at once. First getting behind the ball on your approach and second moving in to your volleys. Moving back behind the T and hitting a forehand or backhand is easier then at the baseline, so it can also be used to help the player understand and learn the proper movement without having the pressure to do it from the baseline which is more difficult when you first start doing it if they are having trouble with it. Its a great drill and I use this one quite a lot.