I usually agree with tom, but here is another one that just doesn't add up to my experimentation (and there has been quite a lot with dry milk!). To me the dry milk addition is TOTALLY different than bringing up the hydration.
I know that Tom has a bias against milk in pizza dough, especially in the fresh form, and I know how meticulous you are on these matters, so I will defer to your experience on this one. Tom also does not like fresh eggs in pizza dough. I believe he is concerned about cross-contamination and health department issues when using fresh milk and eggs that he fears may end up shutting down a pizza operator, even if only for a short while until the problems are corrected. He often discusses using the dry forms of milk and eggs, which should be free of health/handling issues, but he believes the added costs are too high. The only chain of any size that I am aware of that uses milk and eggs in their doughs is Donatos. They used to prominently promote the milk and eggs in their doughs in their advertising but they no longer do so. I believe that they still use milk and eggs in some formsin their doughs, but the doughs, in the form of skins, are now delivered to their stores in frozen form.
Thinking back, I believe the last time I used dry milk powder was to make a clone of the original Pizza Hut pan pizza, not the current one that no one seems to like. I was working from an old PH pan pizza dough ingredients list that I tried to convert to baker's percent format in the right pecking order to make the dough. I used the same dough ball weight that PH used for its smaller pan pizza. From my notes, I see that I ended up using only about 1/3 teaspoon (0.50%) of nonfat dry milk (baker's grade), which was perhaps too little to notice its effects. I also used whey and buttermilk powder. I even hunted down some pure fructose that was called for in the ingredients list. I was not particularly satisfied with the results, so I decided not to pursue that style further until I had a better idea as to how to proceed.