Encounter.diagnosis.condition includes reference to condition or procedure. Since QI-Core created a separate Encounter.procedure extension modeled to allow specification of a principal procedure (rank = 1), the Encounter profile provides ambiguous direction as to whether Encounter.diagnosis or Encounter.procedure (extension) should be used. Since US Core does not include Encounter.diagnosis as Must Support (and only inherits the element from base FHIR), change the the reference for Encounter.diagnosis reference does not require a variance from US Core (confirmed with Brett Marquard and Eric Haas on the CGP WG on September 9, 2021).
Secondly, the mapping from QDM "Encounter, Performed" diagnosis.code maps to Encounter.diagnosis.condition and QDM "Encounter, Performed" procedures maps to QICoreEncounter.procedure.value[x]. Therefore, the QDM to QI-Core mapping is consistent with the distinction (I.e., not to use Encounter.diagnosis.code to reference a procedure). Thus, nothing needs to change in the QI-Core QDM mapping table.