In section 3.9 ProofApprovalResponse, it says that a ProofApprovalResponse is required when a ProofApprovalRequest is received. In the 9/26/19 PrintTalk meeting, it was decided this should not be required.
If a Print Buyer receives a ProofApprovalRequest, it SHOULD
SHALL send to the Print Provider a ProofApprovalResponse whose
@BusinessRefID SHALL reference the ProofApprovalRequest and contains the Print Buyer’s approval or rejection of a proof.