... O-Sensei came from a certain background, with certain beliefs, so some things would affect him in different ways (I expect) from somebody raised in a different manner.
As far as I know there is a group of certain kiai which are common to most/ (all?) ryû. And there exist additional kiai which are only used in certain schools. As far as I know, it was especially the first, common, group Ueshiba referred to when talking about kiai?
When I learned to sing and to speak, I learned about the different ways our body uses to form certain lutes (sounds?). And you learn how different lutes (sounds?) affect you yourself and the person who hears what you sing or speak.
The body is connected to the sounds/lutes: Producing them and perceiving them.
And our emotions are affected to the sounds/lutes.
The effects are comparable. So maybe it is not a question of personal context?