Custom search param with multiple bases returns wrong type in results

[jamesagnew]

Per an email from Dave Carlson:

I defined a SearchParameter with 2 'base' types, MedicationRequest and ProcedureRequest. Searching with either base will always return instances of both types. My understanding is that only the resource type used in the search should be returned, e.g. for [base]/MedicationRequest?reason=[condition-id] only MedicationRequest resources should be returned. My SearchParameter resource is copied below.

Here is the SP:

{
        "resourceType": "SearchParameter",
        "id": "cc-request-reason",
        "url": "http://clinicalcloud.solutions/fhir/SearchParameter/request-reason",
        "name": "reason",
        "status": "active",
        "publisher": "http://clinicalcloud.solutions",
        "code": "reason",
        "base": [
          "MedicationRequest",
          "ProcedureRequest"
        ],
        "type": "reference",
        "description": "This parameter filters Request pattern resources by reason reference",
        "expression": "MedicationRequest.reasonReference | ProcedureRequest.reasonReference",
        "target": [
            "Condition",
            "Observation"
        ]
      }