Of course many, even most, painters do sketch what they intend to paint, likely that's the predominant technique.

But it's not universally true, particularly among artists working in the last 100 years or so. Certainly Jackson Pollock (whether one regards his work as good or not) didn't sketch out how he was going to distribute paint onto canvas. Another example is Morris Luis (and other "stain painters") who didn't sketch out how he applied paint to canvas.

You're comment is largely correct, just pointing out that more than a few "decent artists" didn't (or don't) work that way.

Humans even have the creativity to come up with sketching.

Models don't have intelligence, even less so creative thinking.