I don't know, a lot of these guidelines seem to be arbitrary. It's good practice to keep code small and to the point, but to say that a class should never exceed 50 lines of code is a little too exact and makes the whole list a bit suspect.
I really dislike religious guidelines like this.
I don't like religious guidelines either. Though if it is used as intended -- a calisthenic -- it is like doing push ups. It makes you stronger. You'll need to do other exercises in order to round out your abilities. That's my take on what this is, not fervent stakes in the ground.