I doubt that’s why you hit the ball fat with this method. It’s more likely that you’re doing something else to compensate for the setup. Jim himself rotates when demonstrating his swing and rotation alone will not drop the club head.
I'm a mid handicapper. I love the feel of Pro V1, but when the ball lands on the green I typically get 6 feet of back roll. I don't like it. I now use Tour Soft balls and when they land on the green they usually stay no more than 3 feet from the ball mark, either a little in front or a little behind. I prefer this. Cheaper balls like Titleist Velocity hit the green and continue rolling forever.
I don't know how to link. All I did was google Jim's swing and found 10-15 short video lessons from him. If that's to much trouble for you, then forget it. Also, you can definitely hit it fat with his swing. Out of curiosity from this thread, I found his videos, and tried it at the range. Hit it fat a few times. I think, because as a "rotational" swinger, I instinctively want to start the downswing with the "rotation" of the my body. With Jim's preload set up, by doing that my club would just dump straight to the ground. I only tried 20 or so swings. It was almost screwing up my own swing because I trying not to rotate, which is the exact opposite of every lesson I've had, my wife has had, or my (2) kids have had.