I believe that program is written for the genetically average male. An average male is the MOST COMMON lifter there is. Pros are the freaks, the rare ones.
Hard gainer is another word for it. Most of us are hard gainers. Pretty much ALL ectomorphs are. I'd even say alot of endomorphs are as well. They gain weight easy, but not muscle weight like they want.
most lifters, hard gainers, will get the best results off of his program of only 3 lifting days a week.