Well...I had a jodo sensei once who said, to a student who was intellectualizing his experience, "Don't think -- do!" I think that was good advice -- yeah, it was a "shut up and train", and it was absolutely appropriate. Furthermore, I think that that's advice that applies very widely -- almost universally. I don't think it's just "some people", but the large majority of people -- as close to "everyone" as makes no difference -- who need a lot of doing to anchor a very little thinking, and that if you don't keep the proportion of doing to thinking waaaaay high, that's where the confusion comes in.
Well said, Mary! I can attest to what gets the most accomplished in "training" between thinking and doing: definately the doing. The mind organizes input and can help us to re-evaluate older, pre-existing sets of experience. However, without that experience, the mind is essentially blind.
For me the bottom line to learning Aikido has to do with the fact that to physically act well people pretty much always have to practice
acting well ("doing things good," as one friend of mine would say). You can use insight to cut to the chase, but you still need to develop the muscle memory so you can perform the action without thinking it through. For a strong mind-body you have to have both mind and body as engaged as possible, and focusing on only one generally takes away from the other.
As it relates to vague phrases like "extend your ki," I come from a somewhat constructivist stance on learning coupled with a strong affinity for immersion tactics so I have no problem when people start telling me to do things I have little understanding of. It's demanding, but that's the beauty of the teaching tactic: it demands greater engagement which in turn promotes greater returns...theoretically. It does often require strong "scaffolding" to keep the student engaged and progressing (it's amazing how many people, when after thinking, "I don't get it," simply stop trying).