Several disciplines, like Ergonomics, Marketing, Anthropology, Sociology, Material Culture, address people's needs and desires, sometimes to an individual level of customisation, their social relations on macro and micro level, their sense-making loop with and by artifacts: why does Design Science need its own designerly understanding of Human Diversity (HD) both in research and in implementation? How do the epistemological constructivist stages of Design matter to answer HD? How does Design Science, in its ontology, understand HD differently than other sciences? What is the role of Design's approach to HD in striving for Sustainable Development? This speech aims to address these questions through practical examples, highlighting the Design tools, methodologies and approaches employed. A Design for All approach is proposed where multiple stakeholders are seen as Real Individuals within their roles in selected Value Chains, and are addressed by Aspirations, Necessities, Abilities in the specific Product Service System Design context, rendering apodictic clustering useless, the Limit Experiencer meets the challenges of percentile deviations, and designed integration minimises up to elimination of Functionally Accessible Social Discrimination.