That article brings to mind henkster's point from a while back that German commanders experienced on the eastern front advised Americans planning for a future war with the Red Army that, whatever they do, don't let the Reds establish beachheads across rivers. That advice appears to be easier given than successfully followed.
Yes, it is. In some places, like the bridgehead at Kanev, the Germans have strong defenses in place, and are inflicting horrible casualties on the Soviets trying to break out.
But they are not strong everywhere. Several small Soviet bridgeheads have consolidated, and are growing. The Germans probably had the strength to hold the Wotan Line if they had conducted a phased, orderly withdrawal to prepared positions instead of throwing away their last strategic reserve in Citadelle. But the battles around Orel and Kharkov, while very costly for the Soviets, burned out the Wehrmacht. Their retreat to the Dnieper was a hasty one, there were no prepared defenses waiting for them, and even if there were, the soldiers the Germans needed to man the line are already dead.