It is another way of saying the same thing, but this is the beauty of Greg’s system. Greg is teaching you the shape for the notes where you’re not relying on the volume of air passing through the lips, you’re learning the shape first passively and then you’re adding the volume of air later for blowing sound out of the instrument.

Greg is breaking the system down because most players are overblowing and playing with WAY too much air pressure and embouchure tension.

Once you learn the shape of the note, then you just add more air compressing while holding the same position via the corners and allowing the vertical aperture to open slightly too get louder.