Then it teaches methods for applying those principles.
So instead of teaching rules, it teaches how writing can be clear. Instead of "don't use passives" it shows when a passive verb makes the writing easier to read. It teaches how much new information to put in a sentence and where to put it. And it shows how to connect this sentence to the next for simple flow.
In any case, this book is great and helped me immeasurably in writing my dissertation in grad school. It gives some advice on sentence structure that I haven't seen elsewhere (like when and why the passive voice can be useful) but also gives a lot of "formulaic" advice on how to organize the entire document. I say "formulaic" because he essentially gives you a formula, which is exactly what I needed and seems to be what you're asking for.
FWIW, I own or have read well over 30 books on writing and this is easily the best one on general---i.e. subject-agnostic---writing.
"Telling me to 'Be clear,' " writes Joseph M. Williams in Style: Toward Clarity and Grace, "is like telling me to 'Hit the ball squarely.' I know that. What I don't know is how to do it." If you are ever going to know how to write clearly, it will be after reading Williams' book, which is a rigorous examination of--and lesson in--the elements of fine writing.