Well, any time you're trying to develop a strong, connected body things like that will happen. Sometimes it gets exaggerated, however, and I think also we tend to look for what we *want* to see. Hard to say what exactly is happening there in that one snippet. And keep in mind there was all the time before that where he isn't in that exact pose. But I will say you can see as things ramp up his arms become more extended and connected to each other to create a more powerful upper body to handle the incoming forces and movements. Or am I missing something?
Points noted and taken. Let me adjust/edit my questions to pertain to bokken work for two-handed use. Why do you think Ueshiba trained that way, though? And I see you used virtually no koryu ... do you know of any koryu that do? I'd expect that they wouldn't train fully that way, but rather have aspects of either hand use.
Well, the problem here is that no one can speak authoritatively about all koryu because koryu by its very nature has a *lot* of things that are private. As an example, Toby Threadgill is a remarkably open and generous teacher in his seminars. However, it is understood that much of what he is teaching at the seminars is more or less "outer" stuff. The more detailed and in depth aspects are for members of the ryu only. And for all I know there are things only taught to the subsequent future menkyo holders. So no one can speak authoritatively about this stuff because so much is hidden.
That said the important distinction to make is whether you're training with a bokken to learn something about aiki and/or the bokken *or* if you're training with a bokken as a "substitute" for a live blade for reasons of training safety. If you are doing the latter holding a blade one-handed isn't a great idea if you're in a full-on contact conflict (or with a bokken). You won't be holding it long because not only can someone swing with more strength using two hands but they are also dramatically faster given the ability to "lever" between the hands. Watch T. Kuroda do his sword work. Or Toby -- the guy is not only fast but smoooooth. The blade move extremely quickly in both hands and you give up a lot going to a single hand grip. If you want a one-handed sword, well, that's what your wakizashi or tanto is for. There are the nito schools but again, katana in the right hand, wakizashi generally in the left. That's how they're worn, that's how they're drawn. And while "that's how they're worn" seems like a silly reason for a lot of stuff, the fact is that experienced swordsmen really don't argue about the which hand goes in front because it is one of those incredibly irrelevant things. Do it long enough and you realize it is a two-handed weapon and which hand is forward not an issue.
Now if the question is training with a bokken *as* a bokken, well, you do what you do. I don't personally know of any koryu that do much of anything left handed single grip with a full sized bokken. It is entirely possible, but I don't know of it.
But if we're talking about exercises, training, ki development, etc. then yes, I can think of instances where we've trained that way. But that is very different from classical swordsmanship which brings me back full circle -- what's the point of the question in the first place? Most koryu that have a sword component work very hard on good swordsmanship. And things tend to stay relatively consistent on proper sword grip and usage for learning it as a bladed weapon and not as a wooden club.
To me comparisons here make little sense. If the training with the bokken is ki development then you do whatever you do. If the goal is learning to use the sword, well, the weapon itself imposes some parameters on what you're going to do. So I'm a bit lost on why this is an issue or being brought up.
If you find some legit people doing "left handed" swordsmanship (which I suppose means someone drawing it from their right side), by all means I'd love to see it. Or one-handed katana usage. Like I said, some schools have "two" sword techniques (nito), but that's pretty much a different animal entirely. And the katana (the full-length sword) is always (as far as I've seen) in the right hand.
But again... I'm not sure what this has to do with aikido, training, or anything else. I don't see the connection.