I don’t think Rippetoe is saying that a gallon of milk a day works better than steroids.
As Kalle touched on,ANY novice who starts out on a regular weight training programme (even a half-assed programme written by any idiot) and consumes a lot of quality protein and calories,
is going to dramatically increase muscle mass and the weight you are lifting.
That is a basic physiological response to starting almost any resistance training and your body simply adapting-It is a mind/muscle connection responsible for many of the initial gains in strength (neural/neurological)
Most novices do not take steroids and they would not see all of the benefits.it is usually frustrated lifters or other athletes who need to break through a plateau,whether it is a certain weight they want to be or a weight they want to lift,increased vascularity,personal best,etc.
In this respect,even someone who had been training and eating for a few months regularly would not see better gains in size and strength merely from drinking or even adding a gallon of milk than they would from steroids.
My Two Cents.