To be clear, HL7 is a not-for-profit organization which has created several sets of standards over its history (HL7-V1, V2, V3, etc)--those standards are probably what you are referring to. HL7, as an organization, is very much a leader in this space.
FHIR, which is what Apple is using, is its own standard, (created/managed through the HL7 organization), and addresses most of your concerns (https://www.hl7.org/fhir/)
FHIR, which is what Apple is using, is its own standard, (created/managed through the HL7 organization), and addresses most of your concerns (https://www.hl7.org/fhir/)