Speaking as an old fogey, I'd guess that what you call "prewriting" is what used to be called writing.
I didn't really have the luxury of sitting in front of the typewriter for many hours a day. Get home from work, make dinner, wash dishes, have a little time with the wife, then get ready for bed because sunrise always comes early. If I wanted to sit up & write for an hour, it certainly wasn't going to be on the machine, or I'd likely cost my wife sleep (& likely the people upstairs as well).
So I'd write. If a dialogue was especially vivid in my mind, I'd jot that down. If a descriptive panorama opened up before me, I'd write it down. It didn't matter where I was in my WIP; seems kindly foolish to think, "Oh, I'll remember it later when I need it."
Right now, I'm working on a novel, a nonfiction, & five shorts. What "order" are they supposed to be in?
I don't write to see the story unfold in front of me. I already have a pretty good idea of the story I want to tell or the subject I want to teach. (Few teachers say "Let's just review arithmetic & see if we end up at calculus, which is what you signed up for.") My experience is that few people are capable of telling a long joke without remembering they left out some important root fact of the premise -- I can imagine what their novels would look like if they tried to write linearly.