Can't speak directly for the Airbus but sounds like they were just trying to slow down on approach - perhaps due to an ATC speed request or in order to get below a flap limitation speed to extend further flaps.
Using speedbrake at low speeds has little effect but it can help if you're not far off the desired speed and might save dropping the gear early and dragging it in. However speedbrakes with flaps out does cause increased airframe vibration and isn't recommended with larger flap settings which is probably why they were retracted as the flaps were extended further.