I don't think that is the primary reason. I think that GT along with just about everyone else plays games with the academic profile of their admitted freshmen. The rejected students who transfer in have typically slightly worse standardized test scores, AP classes, etc... so they are not included in the freshmen class if they transfer in. Your typical freshmen, from metro Atlanta at least, has a 1500 SAT score and 10 - 12 AP classes. Having one or both parents having attended GT means nothing anymore regarding admissions and the GT admission office will tell you as much.