I agree that the equation stood out as being nothing short of "bold", but he did say "all things being equal". Obviously different athletes/lifters at different levels (novice, intermediate, advanced), with varied diets and supplements, hours of rest, and even mindstates will make different kinds of progress in the lifts due to things like added mass, more concentration or better technique. All the variables in the world make it pretty much impossible to come up with a solid formula to follow, but I think it was more of a guideline and a path for people to follow - get stronger, and you will get bigger.
The only thing it didn't address was triples and below. A lot of olylifters don't get too big (though, they're not tiny) and they train mainly with triples. Any type've training like that focuses on the nervous system more, and you advance through better, oh what was it called? I think rate coding, among other things. Either way progressing in, as madcow2 puts it, "appreciable rep ranges", will net you more musculature.