Yes, it uses HOLD invoices.

There is a limit to how long they can be held, so once it gets close to the end if you haven't consumed much energy, I have to settle the deposit even if you haven't unplugged the charge cable. The time is long enough that you should have moved your car by then so it also serves as a penalty for not moving your car and allowing me to generate revenue from someone else.

If you unplugged the charge cable but haven't moved your car, I don't have a way to detect that, so you can pay the exact invoice and get the deposit returned and I no longer have a way to penalize you for taking up the space, but that is a risk I have to take.

If you unplugged the car and left without paying the exact invoice, someone else can use the credit that is still there from the deposit until the time expires.