[allenphoon]

sorry, as i didnt read the whole passage and straight reply you once i saw the question

why you make the upper cut? since roots have the potential to form between these layers(space between lower cut and upper cut), and even if roots did not form at that layers, there still got some cells storing nutrient and cell function as photosynthesis unit that supply the most primitive energy to the plant(except the wooden stem).
Furthermore, if you do not make the upper area, but only creating the lower cutting, it will be nice, since plants will have more space for root growing or more area to be covered by propagation media such as water, sphagnum moss, peat, etc

just my opinion, no mean