Good example of correct physics but wrong conclusion. Reminds me of the sports scientist podcaster that claims running on flat road has no mechanical power going on and means zero work.
"Strength" riders, use low cadence, choose longer cranks and use broad muscle groups at more angles of the stroke cycle (especially glutes and calves at the 12 o'clock). Their feet move SLOWER - because the cadence is lower and ride style smoother. These guys normally have the saddle further back and have their torso higher. many triathletes also gravitate to strength riding when going uphill by shuffling backwards in the saddle.
"Spinner" riders treat the chainring as a flywheel and twitch their thighs up and down with a smaller range of hip and ankle motion. They could benefit from short cranks. These guys are typically further forward over the BB and have less glute and calf activation.
As a low, aero position that doesn't tire out your posterior chain is beneficial for overall long-course performance, shorter cranks (--> spinning) might improve ironman/70.3 performance in most people, in the short term. But only in the same way as if you suddenly only did all your run training on a track with super shoes.