Rigid mutually exclusive categories misdescribe people of mixed ethnic or religious background.

Evidence

This is closely related to problems with typologies. One of the standard rules for creating typologies is that the categories should be mutually exclusive. Mutually exclusive is fundamentally a dichotomization rule. The Conceptual Overlap Guideline rejects this and says that one should allow membership, partial at least, in more than one type in the typology. For example, many people are partial members of different ethnic or religious groups because their parents come from different backgrounds. — Gary Goertz, Social Science Concepts and Measurement, 479

Categorization

• XREF: Connects to identity and hybridity material — e.g. The Namesake and The Reluctant Fundamentalist, where protagonists straddle two cultural categories that institutions treat as exclusive. — connects to: Lumping all non-Black multiracial people into one category erases their distinct experiences. — Tatiana I. Zamora and Amado M. Padilla, Making sense of conflicting messages of…, 51
• DEFINE: Clarifies that ‘mutually exclusive’ is itself a dichotomization rule embedded in standard typology practice, and that Goertz’s Conceptual Overlap Guideline explicitly rejects it.