I guess so. But there's no forcefield glow across or around the Spacedock doors, and the glow within the Excelsior
cavity is indeed within.
Really, with craft as big as those putatively docking inside the Excelsior
rear entrance, atmosphere probably wouldn't be necessary or even desirable. The craft would have more versatile means of embarkation than the tiny shuttlecraft do, such as proper docking ports and transporters of their own; no need to provide for people who walk in through the side door.