I'm not finding the idea of thinking of each weapon as working in a certain dimension helpful, but... I do think it makes some sense to think of particular attacks/strikes/movements that way, and to analyze the shapes described by the weapon during the attack... just not entire weapons. As I said, my experience is limited, but since we're talking about what's helpful to beginners I might as well say what I as a beginner find helpful. For me, if people give me an analogy or rule like that I tend to get more confused if everywhere I look I see so many exceptions.
My feeling is one should teach people properly from the start. Dumbing stuff down and over-simplifying to make something comprehensible for beginners that is actually far more complex doesn't do anyone any favors. Beginners are generally quite capable of understanding more than they are apt to be given.
It's rather like the time I was at the Zoo with my young kids and we were looking at the Great Apes, and the Orangutans in particular. My kids could have named them all properly plus any number of the monkeys in the complex next door. A couple was next to us at the same time and they told their child to "look at the monkey"... That child was perfectly able at that age to recognize and remember the differences but they didn't bother (I am being charitable by assuming they actually knew the differences themselves).
It's the same with Aikido. If you make things too simple or make things too easy, the beginners like it because they aren't confused and they aren't intimidated. The problem is that later on, when you try to bring them into the reality zone they quit because now it's not what they thought. Everything's harder and more confusing.
We created a VERY user friendly beginner program at my dojo in order to try to raise the retention rate. It has worked marvelously. As recommended by Ikeda and Saotome Senseis, I don't even teach the beginners. It is so basic and "nice" that I find it fairly mind numbing. Not even in the same dimension with how I trained with Saotome Sensei back in the 70's (which was te intention).
However, the problem is that I have been unable to get the beginners to leave the beginner program and start training with the upper levels. They find it intimidating and confusing. So they stay in the beginner classes and have a gay old time. It's like a separate dojo inside my dojo. It accomplished the job of helping support the dojo overall, which from my standpoint is important. But I have never liked the idea of a sort of "class system" in Aikido, which in my opinion we have, where the folks on the bottom of the pyramid are there simply to support those of us who are at the top of the pyramid. But because we made it so safe and so nice up front, we attracted people who want safe, simple and nice. They don't want to change that. Did we do them any favors by doing that? I think maybe not...
That's why I think it is important on the forums to keep the discussions straight. There are any number of folks who read these threads, far more than actually ever post, and they read things that seem authoritative, written by someone who is running a dojo somewhere, and if it seems to be on something they don't know much about, they'll believe it and internalize it and even pass it on to others. So, it's important to try to make the information as complete and factual as possible. If that makes it a bit more confusing to a beginner, that's fine. It's complex stuff. Over-simplification on a subject like weapons use ends up just like calling every ape in the zoo a monkey...