
If somebody wants clickbait, but remain objective, then just add "ZOMG, WAT R U DOING WITH UR STEREO SUB?!!1!1ONE"
Popularity comes with power. But power comes with responsibility. Owning your online presence doesn't entitle anyone to spread misinformation.
So, months ago, on here, we came to the conclusion, that unless it's for vinyl, monofying (hope, everyone understands monofying) sub frequencies, is entirely optional and up to taste.
With a professional speaker system, you won't hear a thing in stereo below around 80 Hz.
In case of binaural listening, you will hear stereo sub, but definitely won't localize it. In my experience, stereo sub pulls the mix's stereo image towards the center, and weakens the impact of any element that has sub bass frequency content. If out of phase, it can even be sickening to some people.
Now, in the SIDE, if you HPF sub bass frequencies (preferably only on stereo bass elements; or if on the whole mix, then gotta go linear phase filter), then you may get extra headroom. But you don't have to just waste it. You can try isolating it with a LPF, distorting it, HPF, to remove the sub, and add the new higher harmonics to the rest of the mix - all still done in the SIDE, only, leaving the MID untouched. Of course, with further engineering, you can inject these new harmonics to the MID as well if you want to, so that it becomes mono compatible.
The result can sound very interesting; but (depending on the stereo sub content) even just monofying bass can make the mix sound more free, wider and impactful.
Of course, know what and why you're doing!
I'm not going to try to stop youtubers from spreading bullshit, cause it's impossible. But at least, I wish they would stop making people doubt themselves at what they are doing. Especially wrongfully, or at least, subjectively.
P.s. yes, I know my opinion sounds like you would have to monofy those sub bass frequencies. Well, nope, you don't. I would still compare with and without stereo sub, at least, and THEN decide, which sounds better.
Now, if Efe's video sez, if it's an OOPS(ie) baes, flip da polarity. Then yes. But like this, that clickbait is a no go for me.