Yeah, a good example is my roomie. Him and I are both sitting at 195lbs, both 6'0 and in high school we always had the same size / frame. Now, when we finish at the gym and look in the mirror after our workouts, my 195 and his 195 look a lot different, even with bf% aside (mine's maybe 11%, his 14%). "Genetic potential" is, imo, simply a personal judgement call that too many noobs make a biased, lazy decision on.