My thinking of why they’d reject that is the Schlieffen Plan’s failure. Germany tried an offensive strategy against the French during the Great War, and the French managed to stop them. In their mind, what did work is bleeding the French nation dry in attritional battles like Verdun. After all, they won after these massive meat grinder engagements. They’d see the French as desiring revenge, but unwilling or unable to spend lives like they did during the Great War. The Germans themselves would be unwilling to fight such a war on their end, but that is where pre-built fortifications come handy. The Germans won the last war, so they want to fight the last war, which on the West means a defensive war. That being said, I expect the Germans to want an offensive war against Russia. Or, a war of maneuver to drag the Russians into hostile Poland, the Baltics and Ukraine and bleed them out that way. They’d recognize Russia as the weakest of the Entente powers and want them knocked out first.