I find it to be more about the prinicple of the movement and accessing the core or spine than I find it to be actually useful in reality. There is alot to be learned from yonkyo about connecting your center to anothers and being able to move them in a complex core to core manner. I think this is what is valuable about the technique, not the actualy application of it in reality.
I agree, if there is any 'point' to yonkyo at all it is the study of a principle. The same is true of ikkyo, nikkyo, sankyo ( 1st, 2nd, 3rd principle) Personally I see all of the aikido priciples I practice as leading to the same end - connection of my centre to anothers at a deep and profound level, not just the physical/mechanical level that some seem to focus on. For me the 'aiki' only happens when this deep connection is made.
To focus on the application in combat of any particular 'technique' seems to me to be missing the point of what aikido is about. I may be putting my head on the cyber chopping block by saying many aikido techniques are not that effective against a 'well co-ordinated' attacker, unless they are applied by an equally/superior well co-ordinated defender. When I say well co-ordinated I mean mind/body working in unison from the centre, when I say superior, I mean the defender leading the attackers ki/mind ahead of controlling their body.
Good to see you still posting here,