My point is that what we call conscious and subconscious is limited by our ability to express it in language: since we can't verbalize what's going on quickly enough, we separate those out. Could we learn to verbalize two things at the same time (we all do that as well with say different words and different body language, even consciously, but can we take it a step further? eg. imagine saying nice things to someone and raising the middle finger for someone else behind your back :))

As the whole article is really about the full brain, and it seems you agree our "unconscious mind" producing actions in parallel, I think the focus is wrongly put on brain size, when we lack the expressiveness for what the brain can already do.

Edit: And don't get me wrong, I personally suck at multi-tasking :)