I'm on year 3 of my iPhone 8, with 82% battery health. My total talk time is over 36 days, and I probably actively use it for non-talk tasks for 3-4 hours/day.

In my experience, which included managing and oversight of the operations/budgets for BlackBerry, iPhone and Android fleets with 10-50k devices, early battery death is usually accounted for by poor environmental conditions like temperature extremes. The AFRs didn't change in my experience much at all over time, except that legacy BlackBerries would get battery replacements.

The only outlier was failure rates for Samsung Galaxy phones, which was an operational issue (about 40% more failures if memory serves) -- NOT a defect or problem with the phone itself. They were mostly deployed to field workers operating out of cars or outdoors because Samsung allows a much broader operating range. Extreme cold especially would kick the crap out of the Samsung batteries, especially if they keeping them in outer pockets of winter coats or leaving them mounted to vehicles. Apple is conservative with battery management because the public perception cost of any battery issue is nuclear, as anything Apple is a headline. iPhones have strict shutdown temperatures for both cold and heat. (which make them useless in many outdoor work environments)