Bernard, you are right that she doesn't call out pH for every recipe, or for every step along the way. My take on it -- which may be corrected by others more knowledgeable! -- is that 1) if there are pH targets for a cheese in the same family, they likely apply to any other cheese in the family unless specifically noted otherwise, and 2) if no pH target is given, even for the family of cheese, it may not matter too much for that particular step or that particular type of cheese.
One other thought -- which is implied in my earlier post, but not made explicit -- is that, in general, the problem I face is not trying to get the pH low enough; on the contrary, it is making sure the pH doesn't get too low at a given stage of the process. Again, for some cheeses such as the camembert/brie/etc. types or blues or Cantal, the pH is intended to bottom out, so I find those makes to be much more forgiving.
With a cheddar-type make, I think you can get away with letting the pH go too low in the cheddaring phase; the taste will be good, but the texture will just be even more crumbly, and it will be that much harder to get a good knit. If you let something like a Gouda get too low while in the press, you likely will wind up with something very tasty, but not really a Gouda - it will be closer to a cheddar in taste, and it will be crumbly rather than smoothly flexible. Or at least, that was my experience with my first two or three Goudas, until I got a pH meter and realized that they needed to come out of the press MUCH sooner than the recipe said.
With mozzarella, you have only a narrow window of pH that will work properly for stretching - too high and it won't stretch; too low and it won't stretch. This is part of what makes mozzarella one of the more challenging cheeses!