The missing marking of the top voice is obviously an inaccuracy of notation. In FE, the slur, placed high above that figure, suggests that stems and beam were planned here, but were overlooked by the engraver, perhaps due to the need to correct an erroneous note (one can see traces of removal of d3 at the beginning of the 3rd beat of the bar). The top voice was completed in GE3.
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category imprint: Differences between sources; Editorial revisions
issues: Errors in FE, Terzverschreibung error, GE revisions, Authentic corrections of FE
notation: Rhythm