The point was that importance is not the same thing as urgency, which the parent comment didn't seem to understand.
>Choosing between Unurgent-Important<->Urgent-Unimportant is exactly the same problem as choosing between Urgent<->Important.
Sure, in the other formulation you simply make the assumption that the important task is unurgent, and the urgent task is unimportant, and so they are the same, as long as we're on the same page.
>You have two tasks: A or B. Which one should you work on first?
I actually did address this. If you have time for both the urgent one comes first, if you may have time for only one the important one comes first.
Urgent is not a synonym for important, and the point of drawing the distinction is to recognise that relative priorities can be different depending on context, such as how much time is available.