What about it makes it so inefficient? Do you think it promotes too much arm-based strength? I can certainly see how it might add a whole new set of variables for translating the power of hara, complicating matters.
I can't claim any real understanding, but I do remember a moment after doing some katadori movements where I felt like I gained an insight into how to move with more "whole-body" feel (even though I know my best "whole-body" movements are pretty lousy). Something akin to that maybe?
I face a whole bunch of people who....
"Remember a moment too....gained an insight into whole body feel, or think they felt this thing....or sort of got this feeling....or had this great night when things were clicking...."
and so on and so on.
If people can not recite chapter and verse what they did and did not do,.,both internally. in connection or with aiki and also in waza ...then what does that say?
FWIW, I said wrist grabbing was a grossly inefficient training tool, it takes to long and is no guarantee of anything anyway.
Why spend forty years guessing- under groups of teachers that often treat us like second class citizens who don't understand because we're not Japanese or worse still ...apologize and tell us they only know how to teach by us stealing their technique.
Only to one day meet someone who is better than you and who can explain the how, why, and where ....in English..and save you decades?
All training and all Aikido is most certainly NOT the same..