Why, in the descending chords in the left hand, does Chopin clearly write a slur, while in the performance practice of this étude they are often played semi-legato or even staccato? Perhaps to avoid unintended two-note slurs, but honestly, that doesn't seem like a reason worth the sacrifice to me.
For Chopin's studies, in my opinion, the point of reference is Pollini, and it doesn't seem to me that he does what you are saying. In any case, since there are repetitions of chords, it is almost impossible to maintain a cantabile legato; if I have to play the same notes, I have to lift [the fingers] to let them resonate. As much as one can maintain the legato, it is never like a cantabile legato between melodies with different notes. Anyway, one also helps oneself with the pedal. Listen to Pollini...