Perfectly acceptable baseline foundational rule for a DM who has never or barely ever run a game before and has little to no experience figuring out through improvisation or experimentation how to run negotiation scenes with their players.
But once a person has become more experienced in running their game... they will soon realize that they can make up whatever rules they want for running diplomatic, argumentative, exploitative, or intimidating scenes with NPCs. And this basic rule can and will be ignored then because it will no longer be necessary to have anything this organizationally simplistic for them to use. The DM will have grown out of it. Basically the same as say skill challenges.
But once a person has become more experienced in running their game... they will soon realize that they can make up whatever rules they want for running diplomatic, argumentative, exploitative, or intimidating scenes with NPCs. And this basic rule can and will be ignored then because it will no longer be necessary to have anything this organizationally simplistic for them to use. The DM will have grown out of it. Basically the same as say skill challenges.