The exclusive presence of the accent in FE suggests that it was added by Chopin in the proofreading of this edition (or still in the handwritten base text). The length of the accent is indicated by its placement to the right from the note. Similarly in bar 8, where the sign is not only moved, but also longer.
Compare the passage in the sources »
category imprint: Differences between sources; Corrections & alterations
issues: Long accents, Authentic corrections of FE
notation: Articulation, Accents, Hairpins