Producing good work consistently means you are good overall. Being great means you produce great work consistently.
One of the linked articles in the piece contradicts the notion that consistently being good would lead to greatness. (Well a link to a tweet of images of the article -- https://autotranslucence.com/2018/03/30/becoming-a-magician/). That author argued that while they were consistently very good at body painting (top 5 in the world championships), they were not able to conceive how the 2016 winner produced the work they did in the same amount of time (6 hours). Even though they were improving incrementally, they were so far behind the winner's work that they couldn't wrap their head around what sorts of improvements they would need to add in order to reach the same level of competency. So it was not just a matter of being consistent. Their mental model was off.
That seems to fit reality and greatness more than the original article. A good mathematician does not simply reach the level of Terence Tao by being consistently good over time.