The reason OMEGA tells you this it's because at 16 yo you are still growing and your bone structure is still very tender and unstable so if you get into a program which forces you to low reps and max force like 5x5 it might be dangerous for you, because most likely if you have been doing the workouts with all that volume there's nobody good enough at the gym watching you and that crappy workout you picked from a pro bodybuilder (that actually works with him, for other reasons...) If you are doing all wrong at the 8-12 rep range workouts, I can only expect that by doing a 5x5 routine you most likely fuck yourself with heavier weights, because there is nobody there to tell you in your face how to do everything right...