First aces from the Luftwaffe as opposed to the US? Shocking. After all, the Germans had a multi-year head start in both WW1 and WW2.
Which air force had the best chance for the last ace in the ETO? Oh, wait. The USAAF, RAF, and Soviet Air Forces may not have had enough German aircraft to shoot down to get the last ace.
That doesn't explain e.g. following top aces, first combat unit posting mentioned:
Erich Hartmann, 352 kills, first operational posting was to 7./JG 52 on the Eastern Front on 10 October 1942
Wilhelm Batz, 237 kills, he was appointed adjutant to II./JG 52 based on the Eastern front on 1 February 1943
Helmut Lipfert, 203 kills, was posted to 6./JG 52, based on the Southern part of the Eastern front, on 26 November 1942
Joachim Kirschner, 188 kills, December 1941 to 5. / Jagdgeschwaders 3
Gerhard Thyben, 157 kiils, late 1942 to 6./JG 3.
Peter Düttmann, 152 kills, joined 5./Jagdgeschwader 52 on 7 May 1943
Hans Waldmann, 134 kills, was posted to II/JG 52 on the Eastern Front at the end of August 1942.
Heinz Marquardt, 121 kills, From 1 February 1942, he was undertaking fighter instructor duties and operating with the Einsatzstaffel of JFS 5 in support of JG 2 and JG 26 in the defence of France over the Channel front.
Franz Schall, 116 victories, in February 1943 he was transferred to JG 52 on the Eastern Front.
Bernhard Vechtel, 108 kills, 1942?
Heinz Sachsenberg, 104 kills, was posted to JG 52, based in the southern sector of the Eastern Front, in the autumn of 1942