The statement that the FSH datatypes are identical to those defined in R5 is technically true – as the language must cover the superset of types for the versions of FHIR it supports (and R5 datatypes are a superset of R4 datatypes). That said, we will clarify the statement to indicate that the types available for use depend upon the version of FHIR selected: Data types : The primitive and complex data types and value formats in FSH are identical to the primitive types and value formats in FHIR R4 and FHIR R5 . The types available for use when authoring are dependent upon the targeted version of FHIR.