This only works for guys who have a metabolism to match their appetite, but just about everyone, by the time they reach a certain size, will no longer want to eat the quantity of food necessary to continue gaining muscle.
For those with fast metabolisms, unless they have a huge appetite, weight gain will usually be little to none. For those who have already added an appreciable amount of mass, adhering to this guideline would result in lost mass in most cases--potentially a LOT of lost mass.
I would say this guideline only works optimally for the very small minority and in most cases is limited to either beginners with slow-moderate metabolisms, or if the individual has added appreciable mass, for those with very slow metabolisms.
Anyone who has been around this sport for a while will quickly realize that one of the top complaints of advanced bodybuilders, and even intermediate bodybuilders for that matter, is the quantity of food necessary to not only continue gaining mass, but just to maintain mass.
It would be nice if the body's appetite continued to increase in proportion to mass gains indefinitely, but it just doesn't...not for the overwhelming majority. I have spoken with 100's of guys over the years who have told me how sick they were of eating for bodybuilding. It is by far the toughest aspect of this sport and the one that most often keeps guys from achieving their long-term goals. Anyone can take a bunch of drugs, and most people can train hard and consistently if they really like this sport, but even the most dedicated individuals often struggle with maintaining the type of diet necessary to maximize their genetic potential.
In my case, I wouldn't have gained any weight if I had eaten only when I was hungry. When I first started my metabolism was pretty quick and I had to eat quite a bit just to maintain 167 lbs of bodyweight. If I wouldn't have force-fed right from the start, I wouldn't have gained anything. I know, as I tried for years without any success. It was only after I learned the importance of nutrition and began to eat what was "necessary", rather than what I wanted, that I started adding muscle mass. I had to forced-feed for every pound of weight I gained...all 105 of them.