Study as many pics as you can especially from people who have been teaching the NHE way and on this forum, you'll notice that the head is actually being placed behind the vertical. I'm not bashing anyone, but just trying to get how I feel about this training. I wish I had pics to go along with this, but I feel that I would make people sad or feel bad, and that's not what I'm trying to do. So please bare with me and my thoughts
If no head gear is on the horse, then the head isn't necessarily being placed behind the vertical, but rather the horse may be reinforced for holding the head in the wrong place, or, it is just the place the horse is comfortable being at this time. It's compex and as Miriam says, it's a process...a work in progress.
Cisco was taught "the pose" at the standstill, but it is only a starting point. It isn't a goal in and of itself. In movement, it varies from low and very much behind the vertical, to a more classic dressage position of vertical, or when needed, slightly in front of the vertical. In watching the Walter Zettl videos, he points out that the free walk,the working trot and the extended canter (?)one has to allow the horse to come in front of the vertical for proper balance (or the extension does not happen properly or comfortably). This does not mean the horse is not collected, but it means the movement doesn't require a lot of collection and the horse should be allowed to move freely and comfortably and if that means the nose moves, then it moves.
Tamarack, of course, tucks even tighter than Cisco in the static pose, but just as with Cisco, as I make the transition of that pose into movement, then nature takes over and Tam finds his comfort zone. Again, initially, this is a lower head set and in his attempts to maintain the pose, he will come behind the vertical. But as he learns to move and to bend through lateral work, his head takes a natural position of being more vertical and a little higher.
One of the things I like (no, ADORE) about this forum is that truely, there are no experts. Yes, different people here have vast knowledge, but not specifically in how to make all this work without tack or without bits. Everyone here is exploring. No one here has achieved exactly what Alexander has done. If they had, then I think this would be a far less interesting place, because discussing things with people who know it all already is really no fun. It is instruction...not discussion. I prefer the exloratory discussion that lets me feel like I am breaking new ground for myself (not for others) and not just trodding old, hard ground that has been trampled already into a too familiar road.
A paved highway is great if you want to get from point A to point B in a hurry. But for adventure and challenge, one has to take the little dirt paths where few have gone before you.
I have been midly criticized on a clicker list for teaching a static pose to my horse...but as I explained there, it is just step one. Then it flows into movement and there it changes into whatever it needs to be. When I have done this with Tamarack, I don't just look at the head, but I involved the hind legs as well once he had the head part pretty good. So the "pose" begins to involve the shoulders, the back, the haunches. I see it as a stretching exercise...not just training a head set. So within that stretch, I will not micromanage the head. ehind, in front, or absolutely on vertical is not was earns the reward...it's the try, and ultimately, the involvement of the whole horse in that stretch.
When the first steps of movement come into play, the head immediately changes it's position. Over time, it all comes back together...but in the end, it's not just having the head/back/shoulders engaged in the movement, it is also that they are engaged and yet relaxed. The poll has to e loose and not tense. So if I don't micromanage that once movement is added, then Tamarack (as Cisco did) will find that point where it is loose and relaxed. If I try to micromanage it, even without a rein, the poll tenses as he comstantly seeks the position where I will click...so I avoid that. So if he falls ehind the vertical for time...so what? If he comes in front of it, so what? Eventually it will fall neatly where it should as all the other parts of the movement fall into balance.
So long and short of it, in my mind, there is no harm in teaching "the pose" as long as one does not try to make that pose move stiffly forward. It has to flow forward. Within that flow, it will change many times. Allow it to change. Allow it to flow.
As you say, it is the rest of the horse that ultimately dictates "collection", but I find it useful (so far) and interesting to teach the horse that somewhere around that poll, is a key component to what we're ultimately shooting for. They just don't know to begin with, that I want it relaxed. They figure it out.
Cisco has a lovely relaxed poll. I expect Tam will too, eventually.