Join Date: Dec 2014
Location: Northern California
No, if you must seriously ask the question in this way, the power does NOT have to come all from the lower hand, though an instructor might say this to someone, especially someone that already knows how to SH cast, just to get them to stop using so much top hand, a common mistake when first learning. There is a style of casting labeled Scandinavian style that is modelled closer to the the "top hand just holds up the rod", but it is just that, a style. Dana, the founder of this web site, I know has a story about having some shoulder injury/pain and switching to scandi style to avoid the pain, for example. Some people might say even the style of rod influences this, for example my favorite rods, the deep flexing Meiser MKS rods, are often said to "like a lot of lower hand", yet these rods seem to me to be polar opposites of what the Scandinavian style aficionados seem to like as a general rule. I think Simon Gaesworth describes it more like 60/40 in his spey casting books and famous video. But again, it is just style. While there are different styles and no hard rule, you will probably never see a really good caster that using a majority top hand. But you will see MANY mediocre ones that have a lot of top hand.
In the end, however if someone just starting said they were having difficulties and for some reason you had to give them advice without seeing them cast (a bad idea) if you were to tell them "slow down and use more lower hand" I'd guess for %80 of them that advice would help. You also need to stop the rod, exactly as you might stop a SH cast, on the power stroke, and as a practical matter of learning you have far less opportunity to muck it up by not accelerating to a firm stop by using more lower hand - your body will stop it - than your upper hand. But what matters in the end is how the tip of the rod moves, not your hands, and it is possible to get the right action with differing styles, within reason.