Yes, I had a lot of similar questions. Maybe 'task' is a misnomer? Maybe it's context switching that is the issue. Like talking and driving and having music playing in the background all exist in the same context of operating a vehicle. Just like using a calculator, reading a textbook and writing in a notebook are all different tasks you switch between to study, but are all in the same context of studying.

Side note, Wikipedia claims you can multitask between tasks you are already highly proficient at.