We give the time signature marking after AI, although theoretically, Chopin could have introduced 
in the lost [A]. According to us, it is, however, much more likely that it was an arbitrary change of the engraver of FE (→GE,EE), who did not use the 
marking in the Etudes – contrary to the manuscripts – even once, cf. the Etudes in C major, No. 1, F major, No. 8 and C minor, No. 12. The phenomenon is also present in other pieces, even in the most obvious cases, e.g., in the Etudes in F minor, Op. 25 No. 2, D
major, Op. 25 No. 8 or F minor, Dbop. 36 No. 1.
Compare the passage in the sources»
category imprint: Interpretations within context; Differences between sources
issues: Errors in FE, 4/4 or 2/2
notation: Rhythm