Okay some serious thread necromancy but this has been something on my mind recently.

What about the knot securing the loop which goes through the kurikata?

This would seem to be a problem, in the sense that if the sageo is, as I have heard said, an expedient means for hayanawa, or if it could serve as an emergency tourniquet (also heard from an iai teacher), how are you going to undo the knot securing the loop, under duress?

With this in mind - that is, putting no knot in the sageo and simply running it through the kurikata - the style of wrapping it around the saya to secure it to the obi actually makes sense. Just unwind and you have your expedient tie.

With the knot, it seems to remove any practical use of the sageo.