When I read the itemContext page (http://hl7.org/fhir/uv/sdc/2019May/extension-sdc-questionnaire-itemContext.html), at first I thought it was talking about populating the value of an item with a resource. It wasn't until I re-read the pre-pop page (http://hl7.org/fhir/uv/sdc/2019May/populate.html#fhirpath-based-population) that I understood it was putting the resource into a variable that could be referenced by fields under that group. It would help if the details of how itemContext was meant to be used were included on the extension's page.