So it sounds like this ryu is an example of a school that believes in principle-based training: the techniques may or may not have direct application, but by moving arms and such around in different ways, general grappling ability improves. Is that a fair characterization?
Yes, Yanagi Hara Ryu is principle based. I entered the study of Yanagi as an insurance policy after becoming aware that my Kenpo (6th degree), Escrima (teaching certificate) and even my Jujitsu (4th degree) were essentially dependent upon speed strength and endurance. At the same time I was getting older, slower and less explosive. I needed to improve my efficiency rather revisiting basic fighting (with or without weapons).
It is my opinion that many Japanese arts and even Chinese arts as they are practiced today are deficient in concepts such as angling and zoning when performed in real-live environment contexts where actions are not choreographed. A second deficiency is that there is not enough focus on instinctive training in principles like (1) evade by 1/4 inch against a real knife (2) do not let flash or sound steal your eyes and mind. Most of this video you showed supports my thesis.
If you remember a few years ago, Frontsight Firearms in Pahrump, Nevada advertised that they would pay martial artists to interview with them to become part of their self defense program. I was the guy that moderated the interviews and wrote their initial curriculum. The process to almost 5 months. It is by no coincidence that I hired three Guros from the Filipino arts, and only one jujitsu instructor. Some Hakko Ryu teachers interviewed and several Jujitsu folks. I just had to go with what was going to work within the parameters of my mission. Felix Valencia of Valencia Lameco was chosen as the lead weapons instructor. He was undefeated in Dog Brothers as were every student he had brought to the games up to that point.
I did not put any Yanagi in the curriculum. Yet, I could make most of the curriculum work more efficiently because of the principles of movement I learned from Yanagi. I was Fifty years old and dealing with a lot of egos and 20-30 year olds. Yanagi was my real survival tool. I believe that any Aiki legacy-style that originated from Daito heritage would have had the same potential for me if I took the time to really study the following: Kote gaeshi, Ikkyo, Nikyo, Sanko, Gokyo, Shiho, Ippon Dori and Yanagi-specific techniques like Kiri Tori - Te Kube Skui- Tomoi Sonako Otoshi. These especially gave me an edge when we freeform grappled with a knife. But I never rushed in like a fool on the first face off. You have to look for (1) technical mistakes (2) breaks in timing and/or (3) gaps in concentration.
Still, you get cut. Just try to get cut once and then make the opponent pay the price. Change (shape shift) from the expectations that the other guy has about you.
We studied several knife threats (duelling, ambush, mass attack, etc). Each has their own issues in strategy and tactics.
As a sideline, herein is one of Joseph Arriola's specialties.... if people would just give him a chance and hear him. I have. He can take me to the next level of a 15 year study of knife fighting.