The law of diminishing returns applies just as much to programming skill as anything else. Most programming work is not that hard; for the vast majority of jobs, the point of diminishing returns occurs well before "works 12 hours a day writing code for fun on GitHub". After that point, other skills start to matter more than sheer amount of code churned out. This is true even for e.g. senior R&D roles, where for those with the necessary programming skill the ability to come up with new techniques is more important than a few more hours spent writing code.