Any tank with adjustable airflow will leak if left full and lying on its side for an extended period of time. Kanger tanks routinely leak even if you're careful not to do that.
What do you consider "an extended period of time"? I've got a two sub-ohm tanks with adjustable airflow (Movkin Luggy and Kanger Subtank-mini) that I leave on their side overnight all the time without any leaking issues. In fact, the Kanger has been lying on its side, full, airflow wide open, for
days (I just got a couple new RDA's that I've been playing with), and it's dry as a bone. In fact, I actually find I have more leaking issues when I leave a tank with just a
little liquid in --
that will do it even overnight, and whether or not it's left upright. I actually don't have this problem at all with my sub-ohm tanks, but my Kayfun "weeps" (doesn't really "leak") overnight, and it does it a lot more if I don't top it off before I go to bed. The only time I've had one of my sub-ohm tanks leak on me is when I filled up my Luggy tank but forgot to put the top part back on the RBA head when I reassembled it.
I think it has something to do with vacuum pressure. Gravity is trying to pull the juice down, and siphon it out of the atomizer through the air path. But it can't just flow freely, there's a little tiny hole plugged with wicking material that it has to go through. So it takes a little bit of push/pull to get anything moving anywhere. With just the one way in or out, through the air channel, air can't get in "behind" the liquid to let any liquid out, so if anything is going to come out, what's behind it has to "get bigger" to fill up the space. Air expands and compresses very easily, with just slight differences in pressure. Liquids don't expand very much, if at all. With just a little tiny air bubble inside the tank, the air can't expand enough to let any liquid come out, and so the vacuum pressure helps to keep gravity in check. But when the tank's almost empty, and there's a much larger air bubble in there, it can expand a lot easier, allowing greater range of motion for the liquid, and gravity is eventually able to pull just enough liquid out to make a drop. Once that drop is out, a little air bubble creeps in to take up the space it left. This little air bubble floats up to the top and merges with the air inside the tank, equalizing the pressure, allowing further expansion, and starting the whole process over again. That's what I think happens, anyway. I don't have a career in fluid dynamics, but I've got my Physics 101 down pretty square.