of course its BS... look at some of the old school workouts. you only need a few basic moves to build muscle. The BS started with people like WEIDER. VOLUME....6 day a week training till your joints screw up. Any young Guy who is full of fucking piss will grow on a very Basic routine if he trains progressive.
I put my young brother on a routine of porridge & eggs (along with his regular meals), squats, deadlifts, bench, barbell curls, military press and press ups. After 6 months he looked like he'd been training a couple of years!. Doesn't take a lot of effort to build a bit of muscle