There is nothing to understand about that point. It's a linguistic distinction which makes no practical difference.
The prioritisation problem is like this: When forced to choose which task do you schedule first?
The Urgent one or the Important one?
If you always lean towards Urgent things, you will neglect the Important. If you always lean towards Important things, you will neglect the Urgent.
>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.
We are on the same page. It doesn't matter how you label them, if two tasks have equal priorities you have no way to decide which task to schedule first.
Conversely: if you have a way to decide which task to schedule first, then (to you) they clearly have different priorities.
The one you've chosen to do is the task with higher priority! Obviously - because you chose to do it first.
You have no solution to this problem. You are faking the fact that you do. You are flipping a proverbial coin (like the rest of us).