Flying Crane
Sr. Grandmaster
I have no training in Japanese sword methods, so very likely if I picked up a katana, my grip would be wrong for the method. However, I am sure I could still sever an enemy’s arm, or cut his torso in two. Could I hold up against an expert, or even mid-level trained person in Japanese sword? Hell no to the first and likely not to the second. So the details matter, but perhaps not always as much as we are lead to believe, because I am certain I can still sever an arm or cut a torso in half.I'm no swordsman but from what I know (shown to me by a koryu guy) if you don't have the grip you won't have the necessary support to keep the blade in front of you against another swordsman. You risk deviating, so you'll be cutting air and he'll be cutting you. Pretty big deal.
In aikido terms, it aligns your bones with the contact point, so you can use your bodyweight to move around it, which is the point of the techniques:
If you don't grip that way, there will be slack at the contact point and you will need an exponentially higher degree of force and/or movement to produce any effect. And your grip will generally be weaker and easier to escape.
Of course one shouldn't disregard angles completely, it would be stupid to try to throw the guy forward if he's unbalanced backwards. And yes there are optimal angles so it's a bonus when you hit them, just like pressure points (another not so important detail IMO). That said, the fingers with which you grip depend entirely on you, while the optimal angle of the throw (within a certain margin) depends on both your position and the opponent's and can vary a lot, and quickly. I think that you have more margin for error, as well as less control, but yeah it's important to a degree.
So I think what we can agree on is that within their respective arts, the details matter. That is, after all, what higher skill in the arts are built on. I think being dismissive of the details that one art holds as important, is making a mistake.