OK, gotcha.
It seems clear that Stan preferred to use the pages he got whenever he could, at least from the more reliable artists, probably because of practical constraints when redoing the pages would have jeopardized the schedule. Some of the most solid pieces of evidence against the notion that "Stan did nothing" are the many instances where his scripting re-wrote what the artist clearly intended. Sometimes that's glaringly obvious, as in the issue of HULK when Hulk gains the power of flight, which Stan unconvincingly describes as leaping; Kirby's story straight-up had Hulk gaining the power to fly like Superman. As soon as Kirby is onboard with Stan's decision that Hulk doesn't fly, he leaps, Kirby's art unmistakably depicts exactly that (and very effectively, I would say!). Whether Stan's editorial decisions to contradict the art or to insert undepicted explanations and backstory (e.g., I'm pretty sure Kirby would have included scenes of Victor Von Doom's mother if he had intended for mom to be established as a sorceress in the Dr. Doom origin) is debatable, but Stan was without a doubt imposing his own preferences via the script, even if he was working with whatever the artist submitted.

For me, nowadays, that's a big part of the fun of looking back at these stories. When you can detach yourself from the ingrained notion that all these artists were working from explicit descriptions of what should happen, you can spot a lot of examples where the script and the art are not in synch, and deduce what the artist initially was trying to convey, and that's something you can't do with fully-scripted material that wasn't created via the "Marvel Method." For instance, I'm convinced that Bill Everett didn't have any intention of radioactivity-induced enhanced senses when he turned in his DAREDEVIL #1 pages; that was added in the scripting (and lettering). (And you can certainly argue that that detail was fundamental to the ultimate success of the character.) And if that, which we consider to be a key component of the Daredevil lore, wasn't present at the start, it gives more evidence that the artists, even at that stage, were plotting with very little direction, not from the kind of detailed description from Stan that we presumed, as fans of the line, was the case.

When Stan came up with his stories of the initial development of these concepts, I don't think he imagined that readers of the future would ever be looking back over things like margin notes on the original art or deducing things from places where the script was inserting things that weren't being illustrated, and constructing plausible scenarios that conflicted with his media-friendly explanations. And it was, after all, a job for him, and one can't expect him to have retained exact memories of the creative process; a good story is more valuable in the hype world than a nuts-and-bolts description of what was, to most involved, a commercial product development, not a work of art that would one day merit a historian's attention and analysis.