I think it is important to hash out how the question should be framed.

Do we want to produce the folks who devise our national security strategy? Or do we want to produce the folks who devise the military strategy and understand how this integrates with the national security strategy?

ADM Hall starts off by pointing out how many civilians attend the schools, as evidence that this gives the military leaders exposure to non-military folks. The real benefit (which he nibbled around the edges of) is the exact opposite. The benefit is that we give those civilians an opportunity to better understand the military considerations.

It's kind of like when I attended a course on unit level maintenance for our SINCGARS radios. The fact that an Infantry Officer attended a one-week course intended for 31U's did not make the course good by virtue of exposing 31U's to an Infantry Officer. Rather, it was an opportunity afforded to me to better understand the ins-and-outs of my commo NCO's job and taught me how to more effectively use his talents. Same for the civilians at the military schools. The military serves the civilians. Allowing the civilian masters in to better understand their subordinates - that is the real benefit. Not the other way around.