Hmm, the human body is such a complex instrument (as are almost all life-forms, and we are naturally largely similar to the others) that generations of scientists and doctors have specialized in attempting to understand and deal with even so-called minor components of it. Yes somehow a vastly simplified view of any aspect is going to give on insight into all the complexities, with no further effort needed? I don't buy it.
So, while certain basics might be fairly easy to convey to someone and get them started on doing their own research (the "ease" of such conveyance should not detract from the difficulty of getting such insight on one's own), such an elementary beginning (analogous to perhaps the letter "A") does not allow such a beginner to even see what might be possible at the letter "Z", let alone do that kind of stuff, not to even speak of putting the various components together into a synthesis to do other vastly more complex and sophisticated stuff. A simple summary might be: If your body is not ready for "B", work at "A" until it is, and progress in understanding from there on that practical basis.
Is it really vastly simplified? Already in this model you have the following things to master: maximality and minimality of tension, coordination and simultaneity of tension throughout the body, the direction and transference of force from one joint to the next, the timescales on which you are capable of sensing and controlling these attributes and removing conscious interference thereof, and the applicability of all of these things to situations one encounters in martial arts. It's a load of confusing stuff already with a bunch of ways to train it, and it's only just from breaking down a simple model of how far a single human movement can go. Simple philosophy, complex break-down!
And if you can draw parallels to what existing athletes are already capable of without even focusing on specifics like this in their training, it only points out how hard and cleverly you need to work if you want mastery above and beyond what they are capable of.
And yeah, it is like learning an alphabet in martial terms, and writing novels is something you do later. But isn't that the premise here? That there is "Aikido" and "aiki-do", one which is concerned with martial expertise beyond our present ability to express, and one which is concerned with working out the basics of what the body can really do first, after which the expression is a much simplified and less dogmatic issue? So isn't the trouble then finding the way through the basics?
But you can look at the term "internal", and it's totally opaque. Doesn't much hint at qualities you need to work on, how hard you need to work on them, and how they finally combine into athletic performance. When the term "internal" was all I had to go on, I was lost with no information, and now by comparison I am just lost with some information.
But at least with a simple working model, you can distinguish between "Aikido", execution of waza fundamentally linked to an operating model of the body, and maybe in the extreme even conjure "aiki-do".