US Core R4 and subsequent versions limited the MS for MedicationRequest.requester to Practitioner based on FHIR-28382 indicating "For legal prescriptions that are not reported, a Practitioner must be the actual requester of a medication request." While that consideration is correct, it does not taken into account the very specific guidance in US Core Medication List Guidance:

• _A MedicationRequest resource query:
• SHALL be all that is required.
• ​See the General Guidance section for additional rules and expectations for Servers Requiring Status.
• SHALL include all MedicationRequest resources with an intent = “order” representing authorized medication orders directly derived from the system’s orders.
• SHALL include all prescribed and “self-prescribed” MedicationRequest resources with an intent = “plan” representing reported medications
• SHALL use the reported[x] element to indicate the MedicationRequest record was captured as a secondary “reported” record rather than an original primary source-of-truth record. It may also indicate the source of the report.
• When recording “self-prescribed” medication, SHOULD use the requester element to indicate the Patient or RelatedPerson as the prescriber.
• The encounter element SHOULD be supported. Searching by context (i.e., for a given inpatient encounter) will return all medications ordered during that encounter, which can include both medications administered in hospital as well as prescribed or discharge medications, which are intended to be taken at home.
• The category and encounter elements MAY be used together to get the intersection of medications for a given encounter (i.e., the context) that were administered during as an inpatient (i.e., the category)._

NOTE: According to this guidance, to include a patient-reported medication on a medication list inquiry REQUIRES that the MedicationRequest.requester = Patient and that the MedicationRequest.intent = plan and * that practitioner-ordered medications use MedicationRequest.requester = Practitioner. *However, since MedicationRequest.requester does not include Must Support for Patient, there is no requirement that a system includes patient-reported medications and that limits the clinicians from being able to retrieve and view/maintain a complete medication list as described in the Medication List guidance for US Core.
Recommend that this is actually an error requiring correction and that it is not backward compatible. I also recommend that the issue is best rectified by creating 2 slices for MedicationRequest, one for practitioner orders, and that constrains intent to order, original-order, reflex-order, filler-order, instance-order and constrains requester to practitioner; and the second slice for patient-reported medications and that constrains intent to plan and constrains requester to all of Practitioner, Patient, RelatedPerson. This solution would be consistent with the existing guidance and it avoids the conflict addressed in FHIR-28382.
An alternative solution is more complex and involves redefining medication list to MedicationStatement with specific constraints to specifically exclude expired medications. This MedicationStatement option would be much more complicated as it would reverse the direction provided since US Core 4.0.