Hey Mike,
Like my discussion with Thal, I suppose it surrounds terminology. As this is the New divers/considering diving thread, perhaps it's inappropriate to have a discussion on agency training philosophies here (I'm the one that has got into trouble for doing this in the past).
Suffice it to say, that the major differences lie in one agency requiring a finite knowledge/skill base that is required for certification and the others set out what they call "minimum standards" and encouraging their instructors to surpass this level. In this case, anything that's added to the program IS required for certification, at the instructor's discretion.
As far as terminology is concerned, the Royal Lifesaving Society refers to 'Rescue' as 'immediate assistance in the recovery of a victim whom is in immediate danger of drowning.' An 'Assist' is given to those who are not in immediate danger of drowning and who can support themselves on the surface, but require assistance. I believe that the American Red Cross uses similar terminology. The point of the buddy system is to lend assistance to the other diver in eventuality of need. If a person is unable to do so, because of insufficient training, they cannot perform the duties required of them in this capacity. This has been recognized by the greatest majority of training agencies.
By the way, I'm correct in saying that a PADI instructor is currently prohibited from teaching buddy breathing to an OW student. Your textbook does not reflect current standards.