I think that you and I are saying the same thing, except that I tackled Gene's question from the standpoint of the yeast and you tackled it from the perspective of the hydration and the "strength" of the gluten network. But yeast, hydration and gluten development all work together.
The hydration, or degree of "wetness" of the dough, does allow for better openness and airiness of the crust and crumb, as was also noted by Tom Lehmann in the piece I referenced in my last post. A low hydration dough will be closed and tough and simply will not open up as much as one that is more highly hydrated. The development of the gluten network is also important because of its capacity to hold the gases of fermentation better and retain them longer. That is one of the reasons why high-gluten flours are often recommended. Their high-gluten levels translate into a more developed gluten network with an increased capacity to hold the gases of fermentation better and longer. But, it is not the flour alone. The way the dough is made will also be a factor. My simple KitchenAid mixer will not do as good a job as your DLX in developing the gluten, so I may not get as good an oven spring as you will, even disregarding for the moment that I am using a standard home oven and you are using much higher oven temperatures that contribute to greater oven spring. Your DLX will do a better job than my machine with just about any flour, just as a commercial Hobart mixer is likely to do a better job than your DLX.
The yeast level is important, especially at the time of baking, because even though you may have the ideal hydration and the optimum gluten network development, you will not get good oven spring without there being adequate yeast at the time of bake. By definition, oven spring is that event by which the yeast gives up its life as that final burst of fermentation occurs when the dough hits a very hot surface, like a pizza stone. Once the internal dough temperature gets to around 145 degrees F, that's it for the yeast and the dough won't rise anymore. At about the same time, at around 140 degrees F, the starches start to gelatinize, and at around 153 degrees F, they are completely gelatinized but still swelling. Without the right amount of yeast at the time of baking, none of this will matter. There may be some steam bubbles but less than optimum oven spring. As you noted in your point 3, what is also important is to take note of the condition of the dough just prior to baking. If the dough has expanded too much and too quickly and starts to collapse and fall back upon itself, this is a clear sign that the dough has overfermented, that is, the yeast has run out of food, and is heading south fast. The oven spring at this point may be severely compromised.
Jeff, if I understood your comment about the yeast quantity and age of the dough correctly, I think Evelyne would agree with what you said. If I am thinking about the right subject, I believe what Evelyne said was that, rather than adding sugar to a dough formulation to serve as food for the yeast over the fermentation period, she preferred to leave out the sugar and increase the amount of yeast instead.