In US Core, There are four places related to these three DiaganosticRepports (Cardiology, Pathology, and Radiology):
1) In https://build.fhir.org/ig/HL7/US-Core-R4/clinical-notes-guidance.html#clinical-notes, it says that "three DiagnosticReport categories which systems should support"
2) In the same section, next paragraph says "They represent the minimum set a system must support to claim conformance to this guide"
3) In https://build.fhir.org/ig/HL7/US-Core-R4/clinical-notes-guidance.html#support-requirements, it says that "This guide requires systems ... to support a minimum of the three report categories"
4) In https://build.fhir.org/ig/HL7/US-Core-R4/StructureDefinition-us-core-diagnosticreport-note.html#mandatory-and-must-support-data-elements, it says that "The DiagnosticReport.category binding must support at a minimum the US Core DiagnosticReport Category Codes of Cardiology, Radiology, and Pathology. Other categories may be supported."
My understanding is the first one (with wording should) contradicts with the other three (with the wording minimum).

According to my communication with Brett on zulip (https://chat.fhir.org/#narrow/stream/179175-argonaut/topic/Question.20about.20US.20Core.20Clinical.20Notes), The guidance on the profile page is the final word. Systems must support those three categories.

Please correct the wording should support in the 1st referenced section to shall support