"Clinical systems and payer systems SHALL use the specification and workflows defined by Clinical Decision Support (CDS) Hooks to initiate CRD."

"Clinical systems SHOULD use the specification and workflows defined by Coverage Requirements Discovery (CRD) to initiate DTR functionality with payers"

We've already indicated that CRD and PAS are companion specs.  Expectations for those specs are defined in those specs.  The DTR spec shouldn't be setting any expectations around the implementation of CRD (let alone CDS Hooks).