I swear, half of Chopin's pieces are just things he improvised once, didn't bother improving upon, and wrote down. I mean, the very fact that his left hand is just the same pattern over and over again with different chords basically proves it's just an improvisation. That's what you do when you improvise.And yes, I know preludes come from improvisations, but isn't the composer supposed to do SOMETHING with them other than just write them down?
P.S. Surprised you did not include the scale in 3rds in your pictures.