What about the comment that he would apply aiki and "hold" it on them for some lengthy time?
I'm not sure what the question is. If I, say, hold someone with "aiki", I'm essentially using my 'jin' (I prefer that over kokyu because kokyu implies a bit more than just jin and it's unnecessary for this conversation) in accord with Uke's forces to effect the "aiki". The point though is that the "aiki" application is still based on the essential intent-directed jin/kokyu force. I.e, the basis of "aiki" is still going to be the ki forces or the kokyu forces (same thing for all practical purposes). "There are many jins but there is only one jin".
Incidentally, Shioda was kind of an "aiki" (in the technical sense of "ai ki") fanatic and there's one video of his that has him doing about every "aiki" trick you can think of, while teaching a class. I'm reluctant to go literally by everything in his books since his books tend to represent compilations of his views as remembered by various students... and then those books are translated into English by people who may or may not have any real kokyu/ki skills.