Christian, IMO, kokyu ho is not a static exercise. Perhaps we have a disconnect of terminology that cannot be explained without getting on the mat.
For me, static = lack of momentum. I can cheat at kokyu ho (after the first time anyway) by timing my outward movement with uke's attempt to find their balance and come back up into a stable posture, but that's a trivial exercise. I believe it turns the table on the encounter, giving nage a HUGE advantage on 3/4 of their techniques. I feel the meat of any encounter is the very beginning.
I should also clarify that when I read "strong-gripped" I don't think of purely muscled wrist juicers, but of whole body connection grabs that feel strong because they are so hard to move from. This is opposed to the lighter "connection" style grabs that are often done.