Ok I am going to give a try at explaining this;
These programs pretty much give the finger to all the bodybuilding horseshit out there. They are designed by some of the smartest strength coaches in the US; not people trying to sell magazines.
The idea that you need to know is that strength will get you the size that you want. (I.e. if a power lifter were to cut his fat he would be a beast, or look at Mariusz Pudzianowski) You get the strength from, obviously, moving the weights up each week.
What turns people away from these programs are two things, frequency and low number of lifts. Here is the deal with frequency and bodybuilding, as explained by madcow2: back in the 70s every bodybuilder was lifting for like 5 hours each day and hitting every muscle every other day. One day one of them took off a week or two and came back stronger then he left. So he thought, and told the world, that training so much is overtraining and the only way to not over train is to only lift once a week. And there is where the normal body part split came from. The problem is that it takes 3 to 4 weeks to over train, and it is a lot of work to do so. So it is not that doing high frequency is bad, but doing it high for long periods of time can hurt your self. If you look at Olympic lifting you will see that they are pulling from the floor 10+ times a week. A bodybuilder would look at that and say he is overtraining, but he is not. He is not doing each workout to the max so he does not over train. Ok, lol, I am just trying to say – squatting 3 times a week is fine.
The reason for the low number of lifts is because they are the only lifts you need to get strong. All the other bullshit things like cable flys and the like, do not get you strong so they are not in the program. The magazines have overcomplicated everything, and there is no need to. Keep it simple.
Another thing is not going to failure. First is that the benefits from going to failure is out weighted by the facts it takes you much longer to recover. You will not be able to keep up the workouts if you keep going to failure.
Here it is from madcow2 his self:
http://www.geocities.com/elitemadcow1/Topics/Training_Primer.htm
It is a long read but if you really care to know you cannot get anything better.
And his main site:
http://www.geocities.com/elitemadcow1/table_of_contents_thread.htm