> to fit the human hand naturally and no other form factor could possibly be right.

I still think this is correct. "Features" like Reachability, and even Screen Time, are software solutions to hardware problems.

I don't think people would be as addicted to their smartphones if they stayed small. At that size, they were more of a tool, and a means to get something done when away from a proper computer. As the size increased, it became mobile-first, doom scrolling entered the picture, and people started asking if phones were bad of our mental health.