• if using Encounter.locatison.location it SHOULD conform to US Core Location. However, as a result of implementation feedback, it MAY reference the base FHIR Location resource. See this guidance on Referencing US Core Profiles

correct to 

• if using Encounter.location.location it SHOULD conform to US Core Location. However, as a result of implementation feedback, it MAY reference the base FHIR Location resource. See this guidance on Referencing US Core Profiles