Gung-Fu, like Western Occultism, has this unwritten law-never show to the uninitiated. So they put out information,
but they don't give you everything.
For those who already know, will see what is missing.
Yang Jwing-Ming did the same thing when he wrote his Northern Shaolin book. Many of the pictures in the forms were flopped, causing you to see it from a different angle, pointing a different direction. Although if you read the descriptions, he does use N, S,E,W but you really need to know the form.
"My Gung-Fu may not be Your Gung-Fu.
Gwok-Si, Gwok-Faht"
"I will not be part of the generation
that killed Kung-Fu."
....step.