As far as we know, nobody has adopted the curved dip tube as we conceive it. The closest is State, whose tube does curve around at the bottom. However, like all the others, it is closed at the end. The idea of all these “self-cleaning” dip tubes is that the water will exit by small “computer-designed” holes up and down the tube in such a way that the water will be kept stirred up so much that the sediment doesn’t have a chance to settle and instead floats out the hot-water line.
We have reason to believe that this approach won’t work well, unless, possibly, one uses a great deal of hot water.
Our curved dip tubes, which we make ourselves, are open at the end. Instead of keeping sediment stirred up, if that’s even possible, it is ejected from the water heater.
As to direction, as you might imagine, you’d want the curve pointed roughly toward the wall of the tank in the opposite direction from the drain valve so that the water will swirl around the bottom of the tank. We mark the direction of curve on the inside of the nipple.
Now, as I said before in another post, it seems to me that you are hanging out in The Tank too much when you might be learning many of these things elsewhere on the site, which contains a considerable amount of information, to say nothing of a few surprises. Especially check out Preventive maintenance and the Weingarten Collection.