You was right in the 1st place.there is zero point to it any volume fluctuations that people hear on say a sine wave as it hits different notes is either because the sinewave goes out of phase when combined with other sounds e.g a synth with free running oscillators or, it's their room
if anything you actually want to be playing round with the volume/velocities/dynamics of each note as flat subs sound absolutely sterile and unexciting on a 3 way system (2 "satellite speakers" and a sub or 3 way driver speakers)
Even knife parties subs are pretty dynamic.can't say the same for the top end though
in relation to sounds with sub harmonics though like a low saw etc it can sometimes aid in flattening their dynamics a bit especially if they fluctuate in phase alot e.g again free running oscillators but i'd swerve it when it comes to subs and other less harmonically complex sounds,retriggered oscillators
Just watched the vid,in relation to what he is using it for it makes zero sense.it's a feckin sub there is no high frequencies to attenuate.if it sounds too high when you stick your other elements over the top then it's the arrangement or the key you are in,compressing and eq'ing subs is complete and utter fail...................