The earlier start of slur in FE results from misunderstanding the notation in A, otherwise quite clear at this place. A similar inaccuracy in GE is more justified by the mutual relations between the slur and notes in GC which served as Stichvorlage. The retouch of the beginning of slur introduced in GE2 (→GE3) aimed at clarifying the voice-leading.
Compare the passage in the sources »
category imprint: Differences between sources
issues: Inaccuracies in GE, Inaccuracies in FE
notation: Slurs