I would presume the goal is to have an electromagnetic accelerator of inbound charged ions to serve as thrust. You can get limitless power from solar, but propellent mass is a limiter.
Looks like all the designs (unable to find details of this exact one) do temporarily hold the gas to try to ionize it fully, before expelling it. Maybe not too much is predictable ionized at these altitudes? If you accelerate the wrong charge, you'll slow!