Luffy literally couldnt hear it.
it only means that Luffy is either not hearing it for whatever reason or that he simply does not care.
Sanji having better hearing in general, or selective hearing, is debatable. I frankly do not care one way or another.
our acting like since other CoO users cant do as well as Sanji....then the abilitiy doesnt exist ?
the only instance where someone was listening in from afar was Enel and he explicitely used his fruit for this.
The fact Aisa could hear Voices at the very least gives way that this is CoO.
credit were credit is due, but we do not have to spin everything and anything into a haki feat.
this only make people stop taking it seriously.