YES, Horst Buchholz also appears in the French version

Some years ago I added the name of Horst Buchholz to the cast list of the French-language version. Then, somebody erased the entry. But I was right. Buchholz DOES appear (quickly, in a gag shot) in the French version when Pierre Vaneck sings and plays music before the other students.
And the alternate shot in the German version shows Pierre Vaneck among the German cast, in a similar pose.
So technically speaking both actors appears in both versions, first of course as the hero, then, fugitively, as an anonymous student among the cast of "the other version".