1) I haven't yet harvested my first hempy bucket ever since learning about the method, so I don't know. But I have no reason to believe that they haven't. This is just a plant in a container, so roots would fill up all the available volume of the container if you leave the plant long enough.
2) If you water the medium slowly enough, it doesn't go directly to the bottom, no. But if you dump water in all in the same spot, then yes, I think it does. I've settled on using 1/4" tubing as my preferred method of irrigating, because the flow is nice and slow. I aim the nozzle right at the stem. This saturates things slowly before eventually filling the reservoir below. Once it starts trickling out of the overflow hole (or, just right before it overflows... you get good at timing it after a while!), I cut the water off. I only let it seriously overflow once a week. This helps to refresh things, and it flushes excess salts out of the container. Some people overflow it with every watering, but I didn't want to be too wasteful with my drain to waste setup.
2) If you water the medium slowly enough, it doesn't go directly to the bottom, no. But if you dump water in all in the same spot, then yes, I think it does. I've settled on using 1/4" tubing as my preferred method of irrigating, because the flow is nice and slow. I aim the nozzle right at the stem. This saturates things slowly before eventually filling the reservoir below. Once it starts trickling out of the overflow hole (or, just right before it overflows... you get good at timing it after a while!), I cut the water off. I only let it seriously overflow once a week. This helps to refresh things, and it flushes excess salts out of the container. Some people overflow it with every watering, but I didn't want to be too wasteful with my drain to waste setup.