For Gender Identity, the value set binding is preferred, so specific jurisdictions are able to use other codes.  And for codes beyond what is in the preferred value set, we describe our approach of defining a minimal value set here: https://build.fhir.org/ig/HL7/fhir-gender-harmony/branches/main/terminology.html#gender-identity-terminology-gi   For Sex at Birth, the Recorded Sex or Gender (RSG) concept can be used to exchange Sex at Birth.  For RSG, each use case or jurisdiction can define the value set for the RSG in question.  The Gender Harmony Project has not defined Sex at Birth as first-class data element in the logical model.