With reference to gluten development at the time of mixing, in our annual pizza course we use a planetary type of mixer to develop the dough just to the point of having a smooth skin. At this point in of development it is impossible to stretch the dough to form much of a gluten film (window pane), however, by the next morning I have a group of 4 or 5 students gather around in a circle and we stretch the dough using the backs of our hands to form a dough skin that any strudel maker would be proud of. The resulting gluten film is thin enough to clearly see skin details of your hands through it. This is the result of what is called biochemical gluten development. This is also the way dough was made prior to Mr. Hobart's creative invention. Back in the early 80's I visited a bakery in Romania that had a total of 60 dough mixing stations, each mixing station was a large bowl into which flour, water, yeast, salt, a little sugar and some oil were added. The dough was then manually stirred by two men with slightly flattened mixing sticks (think baseball bat with a flattened end something like an oar.) The dough was mixed until it looked like wet oatmeal, and then covered and allowed to ferment for several hours, it was then transferred to a work table where it was given a couple folds, cut into pieces (never mind scaling), placed into beehive baskets, proofed, turned out of the baskets onto sheet pans and transferred to the oven for baking.
As for high gluten flour, technically it doesn't exist as was correctly indicated. Flour contains seven different proteins including glutenin, and gliadin which, when agitated in the presence of water combine together to make the adhesive mass that we call "gluten". As a general rule, the higher the protein content of a flour, the more gluten can be formed from it, but this isn't always the case, and to add confusion to this we then encounter differences in gluten properties which basically put, means that some gluten is strong, and some is weak, some is tight, some is more elastic, and this has been the subject of VERY EXTENSIVE research world wide for over 35-years now, and we still don't know why these differences exist or how to test for them aside from an actual mixing or bake test. Flour is not so easy to fully understand, it is a very complex ingredient.
Tom Lehmann/The Dough Doctor