The distinction he's trying to make is that (working) drawings are exploratory, while finished works are reproduction. The artist draws the subject in the same way that a developer prototypes something: to see what will work, to flesh out requirements and risks, and to capture data about the project; the full build that follows has a clear spec/goal. The author of the piece could have observed that painters often do colour studies as well as prepatory drawings for the same reason: capture data, do a trial run, experiment a little.
Old master drawings are these amazing things to see in person just because they're obviously working documents of the subject and incredibly detailed and polished in certain ways. They're among the most beautiful objects I've ever stood in front of. They have an aspect of egolessness that gets at what you identified, I think: the artist wasn't thinking about style or final presentation or their role in it, but about pure intake of the subject.
Old master drawings are these amazing things to see in person just because they're obviously working documents of the subject and incredibly detailed and polished in certain ways. They're among the most beautiful objects I've ever stood in front of. They have an aspect of egolessness that gets at what you identified, I think: the artist wasn't thinking about style or final presentation or their role in it, but about pure intake of the subject.