Why 'nonexistent people' do not have zero wellbeing but no wellbeing at all

Some believe that the harm or benefit of existence is assessed by comparing a person's actual state of wellbeing with the level of wellbeing they would have had had they never existed. This approach relies on ascribing a state or level of wellbeing to 'nonexistent people', which seems a peculiar practice: how can we attribute wellbeing to a 'nonexistent person'? To explain away this oddity, some have argued that because no properties of wellbeing can be attributed to 'nonexistent people' such people may be ascribed a neutral or zero level of wellbeing, setting the baseline for comparatively assessing the harm or benefit of coming into existence. However, this line of argumentation conflates the category of having zero wellbeing with the category of having no wellbeing. No Φ, unlike a zero level of Φ, is not comparable to levels of Φ - neutral, positive, or negative. Considering the nature of wellbeing and the fact that 'nonexistent people' cannot (metaphysically or conceptually) have wellbeing determinative properties, it follows that 'nonexistent people' have no wellbeing rather than zero wellbeing.