Something the article probably left out is that flip phones had physical buttons with raised edges, so you could feel the back key without looking at it. That changes everything, because your thumb learns the shape and spots it by touch alone. A flat touch screen gives you nothing to feel, so the arrow ends up being pure muscle memory, and right handed people reach for the right side on autopilot. The old makers did not just guess, they had a physical layout that rewarded placing the key where the thumb sat. What bugs me is that we copied the position without copying the feel, then acted shocked when people kept missing it. The fix for your checkout was probably less about left or right and more about making that target big enough that a wrong thumb still lands on it.

Wait, you actually sat there for two hours arguing with a flat earth guy? That is some serious dedication to a lost cause. I usually tap out after like ten minutes when they start talking about the ice wall.