Fun is kind of a slippery word. Because I think “fun” is often used as shorthand for describing enjoyment of a leisure activity. But also some things that aren’t typically described as “fun” can be enjoyable as part of leisure activities. Like, catharsis, for example, can be greatly enjoyable despite not being what I think most would typically call “fun.” But I don’t think that the intent of this passage was to say that a rules change aimed at producing cathartic gameplay experience isn’t sanctioned under rule zero. Language is complicated like that.