I think you are misinterpreting where the fuel consumption comes from. It isn't the reoriantation. That you can do with internal reaction wheels. All you want is rotation, not movement. Turn something inside in one direction and the outside will turn the other way. The only problem is movement for that you need to eject stuff the opposite way you want to go. And that is needed because L2 is unstable. I.e. you roll down over time. Which needs to be counteracted by station keeping. I'm pretty sure they'll use the fuel usage to measure the local gravitational field around L2 and from that update mass distribution estimates around the inner solar system.