I enjoyed your talk(s). But I wanted to note that I've had (recent) experience working with proprietary/commercial audio software development that somewhat paradoxically undermines your description of the role of the developer. Although it may seem strange, some companies choose or are forced to hire developers who, despite having excellent development skills, have close to zero knowledge about the domain they are working in. All the understanding of the workflow and desired goals is left to a "product manager" who defines the required changes/additions, and then the developers are expected to implement them without (necessarily) understanding their purpose.

Open source tends not to work this way, and we generally expect developers to function as de facto product managers (or at least feature managers).