In the various Observation profiles, constraints on .subject are inconsistently applied. Sometimes there are no constraints, sometimes the cardinality is updated to 1..1 and sometimes the reference is constrained to a Patient or US Core Patient (but never to the PH Patient that I recall). Is there a reason for the variation? If not, the same constraints should be applied to all profiles (maybe with a US PH Observation profile that can then be the basis for additional PH Observation types)