Re: hand technique = strike technique
I don't know, it seems a bit trivial to notice that that everything is in some sense up or down or in or out or sideways. We live in a three-dimensional universe, so of course every movement we make in this universe can be broken down into combinations of three directions...
Also it feels to me much more accurate and simple to describe many motions in ways that involve rotations around an axis, and/or translations in space. And most movements in aikido are superpositions of more than one thing (translations and rotations using various planes and axes). I don't think most techniques can be accurately described as simple movements along one axis or in one plane.