I need to stop but....
I think this whiplash subbing is more than just a part of the "system." It is an ego project.
It brings a lot of attention to CKC's distinctive coaching style, "wow, look at her, making all those hockey subs. No one else dares to do that!!!!" {which is what every announcer says every game) and more to the point, it probably gives her and her staff a sense of "active coaching" and control - wow, we are really exerting our influence on the game!!!
I think as she grows into the job, she will learn that less is more. A coach needs to step back in the game, let the players take control and responsibility, which also requires that they understand their roles and responsibilities in the game plan. And that is hard to do when players are cycling out every 2 minutes, playing with seemingly random groupings and given the generic instructions of "go out there and play as hard as you can for 2 minutes! ["But play hard doing what?" may be the lingering question on the players minds].