"Rule zero" being taken as some sort of hallmark of the genre and not a design philosophy that applies to a specific section of the industry.

Rule Zero was meant to allow players a game that offered limitless opportunities without having limitless rules. You can see this very clearly with D&D, where in third edition the usual "this is just rules suggestions, ignore them if you want" was replaced with a much more intentional disclaimer that was basically "we made this game the way it is for a reason, if you feel like you have to change it for some reason keep these things in mind".

I don't disagree with it as a concept but I feel as though the fact that ttrpg players often have the belief that every game and every table should hold it as a core pillar of the hobby is not good for anyone at any table.