Its very true that it wasn't yet as strong as it was designed to be nor was it as strong as the Maginot line. It only had to be enough, though. If Germany's western border had been completely unfortified there would have been no way that the Allies wouldn't have attacked. And even the unfinished wall represented a huge investment for Nazi Germany. If you haven't already I'd recommend reading "The Wages of Destruction" on the economy of Nazi Germany, its a fascinating book for a number of reasons.