Indeed, some labels tout their own unique formulation, so I'm inclined to agree with you.Yes. Remember “Quiex II”, “Quiex SV” and JVC’s Super Vinyl among others? They play very quietly. It takes more than minimizing re-grind to get records to play black quiet.
I would mention that the Dynaflex pvc was (allegedly) formulated to play quietly, and generally they do, but my source is unreliable. To my knowledge RCA has never gone public with the use of an additive for those pressings.
As far as patents including claims or embodiments that never get implemented....it’s smart (defensive) Intellectual Property strategy- claim as much land around your preferred embodiment as you can afford to defend.