What I said is also absolutely true, and required by the laws of physics - in this case static mechanics. If your hands are literally in the same spots, both on the rod, and in space, no matter what you think you are doing, the force on each hand, and the rod flex, is the same. That is all I’m saying. How it feels based on the original intention, or whether you got it to that precise position by lowering your lower hand or raising you upper hand (or waving it about at random before arriving at the same configuration) is a psychological rather than physical reality.
Now if you are in fact in a different, more extreme final hand configuration then I would argue that also might be considered “cheating” in this exercise simply because you could have arranged to arrive at that position by any of a infinite number of routes, including one where the last step was raising your UPPER hand. In this case the hands aren’t really in casting position anyway, so the exercise is not teaching that per se.
Again, I’m not arguing with the efficacy of the teaching method as I’m definitely not qualified to judge that, only at the analysis of what is actually going on physically.
We could also do an analysis of the work done by the leaver action, which has nothing to do with the final load of the rod, the final balance of forces, or the final rod flex. That also is easy to do, and without getting into it I don’t think the analysis is going to be what is implied by SLSS - the lever arms, as he seems to be describing them, have the same length BTW. But even so I don’t think that has any bearing on the original point which I take to be this is a way to load a rod more, not a slightly less tiring way.
Personally I’ve always thought focusing on the lower hand is a great tool prevent sloppiness because if you use both hands, and with varying relative amounts, the actual lever point (hence the geometry of the cast) can move around, and especially as the lower hand is hard limited in its motion helping to ensure a hard, high stop. But these are not physical limitations on anyone with enough discipline that advocates using “both hands equally” like Simon Gawesworth in getting equally good results. FWIW I find that I generally do NOT have enough discipline - or at least consistency. The dominant hand is a harsh mistress.
. So I do find focusing on the lower hand often fixes my sloppiness when it gets out of hand. But when I cast left handed the problems solve themselves.
I think I have discussed this with people in the past, but in addition to lever arms there is the center of mass of the rod and reel, and this is always close to, if not right at the upper hand when casting. So using less upper hand movement and more lower hand movement will have a very different feel than the other way around. Depending on your personality type it may not matter, but you will certainly have to fight the CM inertia of the rod/reel more using a lot of upper hand. Perhaps fight is the wrong word - you will feel it more, but you can also work it into your stroke as well.