This is not exactly a new concept but does have twist I think, I would need to compare them because I am not sure about all the details on the original design. Though your question is basically how big an air
pump is needed to lift lift the water in a 12 liter bucket. Air no mater how little will always rise to the top of water no mater how deep. The question really becomes how much air is needed to displace enough water to water your plants. I have not tried either design myself. Going by the the image at the end of the video, I doubt this design would be able to put out enough water for a good size plant and/or with anything other than a low volume air pump. I could easily be missing something in the design though.
If the P.V.C. tube is air tight, the air from the air pump will fill the tube and push down. That should push water through the tube to the plant if the water level in the reservoir is just right. Though that would only happen until the air level reached the opening to the tube to the plant, then the air would escape through that tube. If the volume of air coming out of the pump is too much the water level in the tube wont be able to rise above the tube to the plant again, so you would only have air to the plant from then on. With a low volume air pump, the water level in the P.V.C. could potentially rise above and fall below the tube to the plant in intervals. In doing so it would be taking some of the water with it to the plant, but in not enough quantity to give enough water for a larger plant.
Though the variables are,
1. the diameter of the P.V.C. tube (wider would allow more water to push back)
2. the angle of the tube to the plant, along with the size of this tube
3. the depth of of the water level (for back pressure)
4. where the opening for the tube to the plant is placed in the P.V.C. (especially in relation to the water level of the reservoir.