But if you'd indulge me a bit more speculation and if you look at some sources for combat methods (both applications and body skills) - if I were in a position to do the research and legwork, I'd probably spend more time looking at the spear for hints at more complete observations (as either physically expressed or embedded at some level in the training paradigm) of internal strength based on the physical requirements of that weapon.
Budd, I wouldn't necessarily disagree with your point there, but with respect to the article referenced, I was trying to suggest that there may be a lot more being said "behind the scenes" by the use of the term "tenouchi" as used within sword arts. In other words it was likely one of those assumed "you know what I'm talking about" deals in the writing. So depending on how you read the term there might be a lot more there than he is being given credit for.
So often much of the good stuff is contained in assumed common knowledge which becomes a problem when someone goes outside the original intended audience or too much time passes and information is lost/changed. Or worse yet if someone who is reading it with ignorance of the alternative meanings and/or self-serving understandings combined with not knowing the source language. So there's not much more for me to discuss on that count as I don't know the language well enough to do what Chris is doing.
I will say that spear work does seem to fit in quite well with much of what I've learned in person from a number of folk so I'd grant that idea. But that itself be confirmation bias of a particular interpretation as well -- it's all above my current paygrade.
But yeah, you start to see connections with stick shaking, spear, ... A very large subset of the same stuff finds it way into sword arts as well, but what I understand of it does seem more "magnified" if you will in the spear/long stick work.