I recently read the memoirs of a Romanian who went to tank school (at Neuruppin) in Germany to become an officer. What I find interesting is that he was both Gefreiter and Fahnenjunker, if I understood correctly, and before becoming an officer, he ended up at Kursk. He was promoted to Leutnant afterwards. Did the Germans have the habit of sending their officer cadets into battle before promoting them? If I understood right, normal officer cadets for the British and the US armies came out of the academy directly as 2nd Lieutenants/Ensigns. How did the promotion system work for the Wehrmacht?
In the Wehrmacht and other Prussian-influenced military organizations such as the Finnish armed forces, officers first spend some time in an officer training school, and then do a "residency" among troops as a Fänrich/Oberfänrich, acting with the rank of a mid-level NCO but doing the work of an officer, typically under the close supervision of an older officer or a senior NCO. The point of this is to train the officers to be qualified to actually do their job from the moment they gain a commissioned officer rank.
In practice, the system isn't very different from the American/British system where the cadets gain rank before leaving the officer training, but are first assigned with a senior NCO who they technically outrank but in practice are expected to listen and obey. I guess the Germans just care more about following procedure and so have these ranks so that their freshly minted officers would be outranked by senior NCOs.