I recently learned something about soaking and it relates to the Nubatama Bamboo 150, a very coarse stone. When I first got the stone I was quite surprised and a little disappointed at how fast the water vanished from the surface of the stone, despite a very long soaking. I tried soaking it overnight with no change, I was constantly forced to refresh the the water supply to the surface.
So I stopped using it for a bit, I tried it again, so it had become completely dry and then I soaked it for about 10-15 minutes and everything changed from that moment on, with a short soaking, the water remained on the surface at least 3 times longer, the difference was quite noticeable and as a result that stone is back in heavy use. I cannot explain it except to say that perhaps when fully saturated it takes on filter like quality, there is nothing holding the water on the surface at all, maybe the internal grain structure is somehow impacted in such a way that the particles become looser but I'm just guessing. I only know two things, a shorter soak, no longer than 15 minutes, (bubbles stop), creates a surface where the water remains for a longer period. That is one thing, the second thing is that this is exactly what Ken told me to do when I purchased it, "let it soak 5-10 minutes...blah blah blah"
So try a shorter soak, 15 minutes and see how that works.
Oh as for the kiwi knives, I have not sharpened one but I have read a Blog somewhere from a sharpener who tested several stones on these knives, they are capapble of a terrific edge from what he claimed.