It is one thing to read what the 'right' running form is. It is another to learn what the most common running form errors are. It makes it much easier to find your run form mistakes.
Then, with the "Imperfect Practice to Find Your Perfect" method, you can follow the form guideline, exaggerate the movement one way, then the opposite way, and discover what is right for you. Try a bigger lean forward, then lean backwards. Try a straighter elbow then a very compact bend, etc.
Posture Running is focused on the 80%+ of the running we all do. That is, conversational running.