I think there are two different ideas being mixed up here. As a developer, there is the code and the vision. Given a particular vision, the differences in developer productivity will be small, perhaps even normally distributed.

However, developers are not simple compilers that translate a human problem into a programming solution. There is an artistic, creative side to the process that can radically impact how effective a solution will be.

To muddy things even more, there are developers who are great visionaries but poor coders and vice versa.