From a recent interview he seems to write 2 to 4 hours per day, every day. That adds up to anywhere between 15 and 30 hours per week.

Personal work capacity will vary. Who knows, maybe he'd write better books if he wrote less? We'll likely never know.

First, best work =/= more work. There are middling returns but you will do more work with more time, at least if you are in execution mode.

Second, creatives have to consider the long term as well. Burnout and writer's block are real phenomenon.

Lastly, yes. Some people are just built different. Maybe you min max exercise and diet and can operate longer than an equally skilled peer. Maybe you have less family responsibilities and truly enjoy your work. These factors tend to target the average, not the top.