After all this I am going with the initial post.
The question is a bout PACE.
If you do not believe that pace is the differentiator then the question is moot for you.
For those that can run a 5K between 13:00 and 18:00, easy runs are done at about 7:00 pace.
When you get down to 8:30 you are at a jogging effort rather than a running cadence.
Anyone trying to put science into this is really over analyzing this relatively unscientific question.