You are just trying to make an appealing argument. This literally adds nothing to the debate. A simple survey of open source software would be more convincing. And even that wouldn't be definitive.
It is an appeal to how logical the example seems. That is, it sounds like it would be applicable "at large." However, evidence seems to show that, "at large," it is mostly a non sequitor.
That is, you get better systems the more programmers you have that do have a good grasp on the whole system. Ironically, you have better arguments against knowing specifics of the system -- that is, at the individual function level -- than you do the high level picture. Consider, Linus knows the linux kernel better than I can really comprehend. I doubt he knows every function's return value.