Interesting discussion. I appreciate your thoughts and disagree with nothing you are saying.
If only we could all attend the same handlers seminar and watch us work our dogs! It's so difficult to draw a verbal picture of my/our successes and continuing struggles.
RD is 2 years and 3 weeks of age. She can't do anything calmly and quietly. Maybe that will change as she ages but judging by dogs like her, probably not. I have a good sense of progress or lack of same in field training. What is less clear is appreciating improvements in (what shall I call it?) street obedience. She vibrates at heel. She remains at heel, but sort of oscillates. And that's an improvement for her because she's dividing her attention between me and everything else in the universe, like at 60 cycles/sec. Tell her down... and her belly will touch the floor but her leg and chest muscles are coiled and ready to launch, her eyes moving to me and beyond me, back and forth, waiting for the next compelling thing at which to launch herself.
Here's the question (that can't be answered.) Is that nature or nurture? Would her working attitude be different, had I begun this and kept at it from the get-go. Her skill level would, for sure. But I think she would always be a dog on the edge.
There is a reason why insanely field bred labs get a bad rap. They're not simple to work with. Progress has to be appreciated using different metrics. She'll never be calm... only more and more self-contained.