Yeah - crossed my mind too...
It's just a happy coincidence I suppose but I've been thinking the same recently.
My someday/maybe list became a list of things to do in another life time - you know like dream achievements to make years from now. Then my current projects list was strictly any projects I thought I could do now, and it soon filled up.
Before long I had a current projects list filled with projects which had no real order to them, and yet some were plainly more important than others. I began to get swamped.
Then I realised I could dump some of these current projects onto my someday/maybe list and come back to them later - after all, they were projects that would keep. This would benefit me in two ways.
1) I could give fuller attention to those projects which were most important at this time.
2) I could free my mind from the swamp and concentrate on practicing GTD using just a couple of projects at a time - sort of walk before I run routine.
Anyhow - that has made a big difference to me, really helped clear my current projects list and clear my head whilst knowing those projects are still there to be reviewed later.
Now of course my next action list is much clearer and appears achievable, I could get the majority of it done this week - if not all. Then I can review and reflect on this progress and develop as I move along.
One question did spring to mind though about your prioritising by urgency.
You set a priority 'Three weeks from when today?' Ok, but then you add other items/projects to the same list and give them a 3 week priority, pretty soon it's just a list all mixed up of some items being 3 wks priorities from 3 weeks ago, and some being 3 wks priorities set yesterday. I appreciate this is probably hard to understand, it's difficult for me to explain!
Week 1 you set a priority for project A for 3 wks
Week 2 you set a priority for project B for 3 wks
Week 3 you set a priority for project C for 3 wks but project A hasn't been started yet... So now you have two projects with a 3 week priority but one is six weeks old and..
Ugh, now I'm confusing myself...
But anyway - I see your point of view.