Re: The brain in your gut
This seems to be related to Ueshiba not liking kata as much as wasa. Wasa gets us early into feeling. Gets us right into gut-centered learning - and with it the "feeling" which we can view as the internal art of aikido.
Karate calls two-man training bunkai. It's interesting that I've had the experience of training with karateka who may have many years of experience doing solo kata. When I work with them on "wasa" - or sort of their version of "bunkai" - they often don't have the feeling aspect in their bodies about what they're actually doing in any given movement.
Ueshiba had great insight into these arts, and how to guide us to the stronger, faster, and more sensitive internal art on a more direct and experiential level.
This also gives us some insight as to why many internal arts shown on video don't really look like much. Especially for those who have little to no experience with arts on these levels.