I grew up in a mining town in Colorado and had a couple summers working for the town digging sewer ditches. Had a couple of older (60 maybe) tramp miners doing the pick and shovel digging as well. I'm not saying they had Aiki but they could go all day while my 17 year old body burned out in an hour. They were relaxed, used their whole bodies, used their connection to the ground to throw the dirt with the shovel and when they hit a large rock it seemed like they never fought the rock, but blended with the shape and usually moved it fairly easily. I think anyone who does physical work over a long time and who is good at it does get some parts of Aiki or they beat their bodies up. It's not trained and from the martial arts perspective there are a lot of elements missing but IMHO there are pieces learned over time to in being good with many kinds of physical work.
Perhaps I am wrong but I think that what mr. Harden is claiming has a totally different quality.