This hasn't been my experience at all. Plumber-developers are generally terrible at architecting systems, whereas confident low-level/algorithms programmers ten

This hasn't been my experience at all. Plumber-developers are generally terrible at architecting systems, whereas confident low-level/algorithms programmers tend to also be very good at designing architectures. Personally, I think it's because development is more fractal than people give it credit for, but I think it's also that plumber-developers tend to be intellectually lazy, which is why they specialised in code-plumbing.