A lot of the stuff Mike Sigman writes is very good in my opinion. I think there are some good things in this blog, but there is a lot going on.
Mike use's the word "normal" to describe what I believe people here might be calling "external". It's another tricky word. Normal to a trained person is not "normal" to an untrained person. All the time I see my students doing weird things that I would normally never do. When I question them, if they've been around for awhile they realize that they are doing something weird, and fix it. If they are newer, I have to spend some time explaining to them why what they are doing is "unnatural" or not-"normal". I use the word normal or natural to mean correct movement, and here Mike is using the word to mean incorrect movment, both are correct usage from our own points of view. That makes this word, "normal" a bad word to use for our purposes.
I remember sitting in Tim Catmell's school one day, and there was this little 4 year old kid running around. Tim was looking at the kid with awe. I asked him what he was looking at, he told me that the little kid had "perfect posture" and it was impressive. I ask if he thought this kid was special, he said no, all little kids have perfect posture, it's not until later that they get bad posture. I asked why, he said he didn't know, maybe sitting at a desk in school or something.
I think what was being outlined by Tim was that we originally learn to move our bodies with great efficiency (this is something Mike talks about in his blog as well), but we learn bad habits as time goes on. Another way to say this might be, when we are young it is normal to move correctly, as we age we learn bad habits which makes our movement worse. Then this becomes normal to us. If we train in proper body methods we can again return to a more correct use of body, and this will again become normal to us.
Hashing out what we mean by "internal" "external", "normal" or "natural" is an important thing to do if we are going to have this conversation. I would suspect most people don't want to do that, so we'll probably just keep chasing our tails.