I thought that he was referring to the concepts as opposed to the drawings themselves. He wasn't redrawing the same subject, he was drawing a bunch of different ones to see which one he should extend upon.
The point you're making is a very good one, though. I, too, noticed how professional artists start with ugly sketches that aren't too different from what I often drew, became demotivated, and just left. But soon afterwards they turn them into beautiful works of art. Crazy.
