Basically, yes.

It was evident that the Western allies would like to get a foothold in Europe to kick out the Germans, and it was equally obvious that this was going to be in Fance. Where, exactly, was an open question. Logistically, the short hop across the channel to Calais was the easiest, so the Germans emphasized the defenses there first. However, the Germans were equally unconvinced that that was the only possibility, so they built "The Atlantic Wall" as part of "Fortress Europe". By the time Overlord was undertaken, more attention had shifted to the West, such as at Normandy, but as Point du Hoc showed, preparations had not yet been completed.

The defenses themselves would do one of three roles. Firstly, to attrit the attacking force and reduce the amount of enemy getting to the beach in the first place. That's the job of the large caliber guns, the anti-landing obstacles, the mines, and so on. The next layer of defense was to contain the beachhead, to prevent the landing forces from gaining room to maneuver, and keeping them bottled up. The third layer was that of the reserve forces, who would move to the landing zone and push the attackers back into the sea. This was the force that was not released by Berlin, no matter how desperate the local commanders were to obtain it. By the time the units were released, the Allies had gained sufficient ground and strength that the outcome was basically beyond question.