Not saying you're incorrect in that assumption (which is reasonable), but odds are the spectrum you're describing would fall in line for GT grads as well. Highest average starting salaries HEAVILY favor engineering and science majors, so it's reasonable to think GT grads would obtain millionaire status quicker than the average college graduate. The fact that GT doesn't differentiate its "1 in 6" (i.e. GT grads have a higher net worth as millionaires, or GT produces more 1st generation millionaires, etc) doesn't make the 1 in 6 ratio anything that really stands out in light of the fact 1 in 6 Americans retire as millionaires.
Basically, a coach from another school could point to the 1 in 6 stat and say, "Son, odds are, you have the same chances of becoming a millionaire if you go anywhere else." That coach would not be wrong statistically speaking.